Yes, you are overlooking some major flaws
I'm only going to address the Major Flaws you're concerned with, since the rest is subjective to both your game play and how people play the class. This should help you get through at least a couple of misconceptions you have.
- Pact Weapon (PHB. pg 108) - You can only have one of these, and due to that, Thirsting Blade can only be used with your one pact weapon. If your DM does happen to allow you to take two pact weapons, that's cool, but is clearly a house rule. Make sure your DM knows about the wording of Thirsting Blade with respect to Pact Weapons.
- You have only one bonus action possible per turn (PHB. pg 189). If you have many abilities that use the bonus action (Cunning action, offhand attack, specific spells, etc) you have to choose which ONE to use.
- Survival wise - largely dependent on magical item availability, your feats, and potion use. If you take fighter at level 1, you'll have higher hit points to start, but your saves will leave you mentally vulnerable. That's why I recommend Archfey pact below, to remove that problem.
The following part is only my opinion on the build itself, and where I would make changes to better fit your stated style of play.
Personal build recommendations:
- Take 3 levels of fighter to become an Eldritch Knight so you can have weapon bond (two weapons bonded, functions very similar to Weapon Pact, allowing for 3 summonable weapons.)
- Instead of Fiend, use Archfey as patron because the up close abilities and immunity to charm are superior for an up close fighter. Especially since Misty Escape gives you a free exit in overwhelming situations.
- Feats - Heavy Armor Mastery, Tough.
You are proficient with it.
While a warlock is only proficient in "simple weapons" you can create any melee weapon and you are proficient with it. Martial weapons often are stronger and have other abilities.
An upgrade for your Mace would be a Flail or a Warhammer which all deal bludgeoning damage, but martial ones have 1d8 instead of 1d6 as damage dice and the Warhammer can be used two-handed for 1d10 as damage dice.
You can create one as action.
This means wherever you go, you are never without a weapon.
You can switch the weapon type to fit different situations (sometimes you might prefer a weapon with reach or a different damage type, keep in mind this feature is lost as you bond to a specific magic weapon).
Also you can indeed create throwing weapons, because they are basically melee weapons with aerodynamics. So while taking a whole action to recharge, you are never out of ammo.
It is magic
In early levels you might not have a magic weapon when fighting against a creature with immunities or resistances versus non-magical weapons. This weapon overcomes such resistances.
You can bond to any magic weapon as pact weapon
This is not restricted to melee weapons, and you have the weapon always ready.
Invocations
Lifedrinker and Thirsting Blade benefit you with abilities you can only use with your Pact Weapon.
Best Answer
Something similar can already be achieved RAW
You mention that you're playing a Hexblade Warlock, with the Pact of the Blade pact boon. Whilst Pact of the Blade only allows the single weapon, this is separate from your "Hex weapon", by which I mean the weapon that you can designate as per your Hex Warrior class feature.
The Hexblade warlock's Hex Warrior feature (Xanathar's Guide to Everything, p. 55) says:
Although you cannot shunt your "Hex weapon" into an extradimensional space like your Pact weapon, both can be used with Charisma instead of Strength or Dexterity. Hence you could duel wield your Pact weapon and your Hex weapon (assuming they are both Light weapons), both of which would use Charisma, which is the next best thing to having two Pact weapons.
Hopefully this suits your purposes, since otherwise you're into homebrew/houserule territory.
Note that if you go with this plan, you can only use Eldritch Invocations like Thirsting Blade with your Pact weapon, not your Hex weapon, so if you wanted to make use of that combo, treat your Hex weapon as your "offhand weapon" and your Pact weapon as your "main weapon", which would then allow you to make 3 attacks per turn with Thirsting Blade and two-weapon fighting.