Paladin 2 / Wizard (abjurer) X

You said you are willing to take at most a 2 level dip in another class for proficiencies. Have you considered taking these levels in Paladin? Assuming you want to keep the "I'm a Wizard!" flavour, taking your first 2 levels as a Paladin of the god of magic (assuming there is one in your campaign, of course) isn't really out of character. So here's my take on this build. I'll mostly cover melee options, since this is what the question is about, but you should still be able to do anything that another wizard could do, just 2 levels later. This gap can be great at certain levels (Fireball is a great damage upgrade at level 5), but it shouldn't be noticed too much on single target damage (Smite!). It's not the strongest build out there, but it's definitely good enough to be enjoyable!

Benefits of 2 paladin levels :

• Proficiency with all weapons : opens up many solid weapon choices
• Proficiency with all armors and shields : although dex is definitely the best stat in 5E, a melee wizard will require spending spell slots on defence to keep up. Being able to wear a full plate and a shield gives great defensive benefits and costs no daily ressources.
• 6 more HPs : While 2 more level wizard levels would've given you 4 more arcane ward HPs, those only replenish on a long rest or by spending spell slots. Arcane ward is an awesome feature, but real HPs trump it anytime.
• Lay on Hands : Yay for 10 free HPs per day! More than makes up for those 4 lost ward HPs, and can be used on other people, too.
• Fighting style : There are many good options here, but I'd go for protection or defence to increase your utility/survival. Great weapon fighting is a good offensive option if you forgo your shield and grab a great sword, especially since you're going to stack lots of dice on those attacks. This can be somewhat replaced by the Elemental Adept feat, however.
• Access to 1st level paladin spells : One thing you'll have as a wizard is lots of low-level spell slots rather early. Smite spells might not always be the best options, but they can add good damage and other effects on your melee attacks. Paladin also has a few abjuration spells, which gives you back some arcane ward HPs, but the good ones are higher level, sadly. If you have the warcaster feat and can handle your constitution saves, Shield of Faith is also very good as a low-cost defensive boost. While Cure Wounds is a paladin spell, you can cast it using your full spell slots, which means that, although not a cleric, you still have access to some great healing powers if they are needed.
• Divine Smite : Convert spell slots into damage. Given that you can elect to smite after you know the attack hits, and that there is no save for this damage, it's a great way to increase your melee damage. Especially good if you crit...

That being said, given equal gear, you should have the same AC as any other tank, since you're wearing the same stuff they are. As for your damage, the new Sword Coast Adventure Guide cantrips are there for you. Sure, they're not going to out-damage a fighter or a rogue, but they're still very good damage options. Since they require a melee weapon attack, they also trigger class features such as Divine Smite, so you don't miss out too much. Having two attacks could technically mean 2 smites per round, but the added damage of your cantrips will compensate for this quite decently.

• Green-Flame Blade : when fighting multiple enemies, this attack basically gives you the benefit of a second attack without costing anything. Since you're not going to have multiple attacks from class features, this is pretty much as good as you're going to get.
• Booming Blade : Assuming you can make sure your opponent moves willingly each round, this cantrip will give you the same benefits as GFB except on a single target.

Other thing to note is that the secondary damage from these spells automatically hits, no save and no attack roll required, which means that you can strike a minion to land free damage on the BBEG. These spells will thus give you decent damage round after round, leaving you with all your other spell slots to use as you see fit. Your 2 levels of paladin will give you the opportunity to convert your low-level spell slots into more damage as an option, and your wizard powers will allow you to turn these same spell slots into defensive abilities. Shield will grant you +5 AC for one round, which is awesome if you attract the BBEG's attention (especially given that your AC is already high). In Elemental Evil, there is also the Absorb Element spell, which gives you resistance against a single element, also for one round. This gives you defensive options for both physical and most magical attacks. As an interesting addition, both of these spells are abjuration-based, and will thus heal your ward for 2 HPs every time you cast them.

And after all this, you're still an almost full wizard. Your access to spells and features will be delayed for two levels because of multi-classing, which shouldn't reduce your melee effectiveness, but you will still have access to 9th level spells and have spell slots as a 19th level caster. While the Signature Spell capstone is good, the real treat is at wizard level 18 (character level 20 for you), so you don't miss out on much. Indeed, spell mastery will allow you to have 2 low-level at-will spells, which gives you infinite Shield spells, for instance. This should allow you to use your slots for more offensive options, since your defence is free. Infinite Shield spells also means that your arcane ward is always topped off after every combat if you take a minute or so to recharge it after each fight.

Your melee power also scale quite decently if we compare them to a tank fighter (longsword + shield, defensive fighting style) of equivalent level :

• Level 1-4 : Fighter [1d8 + str] vs GFB [1d8 + str + (int secondary)]
• Level 5-10 : Fighter 2x[1d8 + str] vs GFB [1d8 + 1d8 + str + (1d8 + int secondary)]
• Level 11-16 : Fighter 3x[1d8 + str] vs GFB [1d8 + 2d8 + str + (2d8 + int secondary)]
• Level 17-19 : Fighter 3x[1d8 + str] vs GFB [1d8 + 3d8 + str + (3d8 + int secondary)]
• Level 20 : Fighter 4x[1d8 + str] vs GFB [1d8 + 3d8 + str + (3d8 + int secondary)]

Of course, a fighter has abilities to increase his damage, but so do you (thank you, Divine Smite)! Since the fighter has more attacks, he's more likely to deal some damage each round, whereas your damage all hinges on your single attack landing. This will be especially important if the fighter can get his hands on a weapon that deals extra damage (like a flame tongue), an ability that would be mostly wasted on your single attack per round. The fighter also only requires only one good stat to be 100% effective, while you will need both strength and intelligence. Since your intention is to go melee, I'd consider maxing strength first, especially considered you'll use your spells mostly defensively or in a utilitarian fashion (so lower save DCs are not as bad).

Feats to consider :

• Warcaster : For pretty obvious reasons (casting and adv. on constitution saves). Combined with Booming blade, it's also a boost to damage: when an enemy tries to get away, you booming blade it, which will deal almost double damage if it hits, as the enemy will likely leave the area right after. If they don't, well, your party gets to kill them anyways.
• Shield Master : If you are using a shield, it's a solid defensive feat.
• Heavy Armor Master : +1 strength, reduce most physical oncoming damage by 3. The drawback is that it doesn't work on your arcane ward, as it has it's own HP pool. As such, any damage the ward takes is not "damage that you take" and does not trigger this feat. Still a great option for a tank, especially one that has a wizard's HP pool and requires strength for his attacks.
• Elemental Adept : You're going to cast a lot of fire cantrips, and this feat allows you to ignore resistance and to treat 1s as 2s. This feat does not specify that only the fire damage dice are affected, so it works on your weapon die, your GFB dice, but also on your added Divine Smite dice. Definitely not bad.
• Mage Slayer : Disrupt enemy spellcasters from melee range. The attack granted by this feat is not as strong as a full opportunity attack (as warcaster will allow for a GFB or BB cantrip), but if you can prevent them from casting, it has a lot more utility. Advantage on saves isn't exactly bad either.

Other things to consider :

• Transmuter instead of abjurer : possible proficiency with constitution saves or resistance to one element is a good trade-off for a melee wizard. Not sure that I'd sacrifice arcane ward for it, though. Since Arcane Ward has it's own HP pool, all the damage it soaks isn't counted towards the concentration save DC. Advantage from warcaster should be more than enough, especially if you have some stat bonuses.
• Bladesinger instead of abjurer : A tough one... Since you're going to use cantrips for offense, you're wasting the extra attack feature with that build. But... a dex-based character wearing light armor will have only 1 less AC than a plate wearing character (equal if you cast mage armor instead), so your bladesong will leave you with a net +2 to AC during a fight once you get 20 intelligence (since you're also forgoing your shield). Even if not going for a strength build, you lose none of the advantages of a paladin (smite, armor proficiencies, healing, spells, etc.), but also gain Intelligence bonus to concentration saves and increased combat speed, as well as overall better skills since dexterity is the best stat. I'd personally favour bladesinger, but both options are very interesting.

Creating custom items is always a matter of negotiation and judgment; there are no hard and fast rules. The books provide some guidelines, but are always quick to point out that they cannot be relied upon, and that the DM is always going to have to judge suggested custom items on a case-by-case basis.

The first guideline is to compare your desired item against the closest available comparable items, and adjust from there. Thus, to allow a ring, such as Devlin’s, to do what the quiver of Anariel does, you would start with the quiver of Anariel as your basis for the cost of doing so.

Furthermore, the passage on page 233 of Magic Item Compendium is really talking about adding new magical abilities onto an item that could otherwise have that ability. But ultimately, you can add anything anywhere as long as the DM allows it. The aforementioned guidelines suggest a 50% surcharge to add something to an unusual slot. So to put the quiver of Anariel effect on a ring should, by these guidelines, cost 50% more. On the other hand, the guidelines also suggest that something that does not use one of the usual magic item slots should cost double, so a magic quiver (which doesn’t prevent the use of other items) presumably costs double. So the guidelines would say that the ring should cost approximately 75% of what the corresponding quiver costs.

However, the problem here is that the quiver of Anariel is ludicrously overpriced, particularly at the regular arrows level. My games routinely ignore tracking mundane arrows in general, so they are literally charging 28,000 gp for a magic quiver that does what any quiver in my games does, by default.

On the other hand, magic arrows are a much bigger deal than mundane ones. Magic arrows partially stack with the magic properties on the bow shooting them, which is a big deal. While I’d say even Devlin’s ring is on the expensive side for mundane arrows, for magic arrows the cost definitely should be much higher.

So instead, I’m going to make a different suggestion: consider magic ammunition as if it were a 50-charge item, like wand. After all, enhancing 50 arrows costs the same as a sword. So if a 50-charge spell-effect item costs spell level × caster level × 750 gp, and a use-activated at-will item costs spell level × caster level × 2,000 gp, you’re looking at the use-activated version costing 2⅔× what the 50-charge version does. So if you apply a 2⅔× multiplier to the cost of 50 magic arrows (which is the same as the cost of a single magic sword), you have at least one reasonable idea for what this effect should cost.

The results are 5334 gp for +1, 21,334 gp for +2, 48,000 gp for +3, 85,334 gp for +4, and 133,334 gp for +5. Most likely you would ideally use equivalent levels of special weapon properties rather than straight enhancement bonuses, though.