Multiclassing Fighter and Warblade
Fighter and Warblade multiclass pretty well. Warblade levels count as Fighter levels (excepting the first two), and Fighter levels count half as Initiator Levels.
That said, Fighter 3 is pretty useless, unless you’re taking the Zhentarim Soldier substitution levels. You probably want to avoid that if you can. Ask your DM to retrain them as Warblade levels, starting early, or perhaps as something else.
Something 4/Warblade 1 is a good break-down because that way you start your Warblade career with Initiator Level 3 – you can take 2nd-level maneuvers right off the bat.
As such, you might take Fighter 4 before switching to Warblade. Another feat is not really a great option, but it’re there (don’t take Weapon Specialization; it’s awful). You could even take Martial Study, to get a maneuver that’s “always readied” (but that you cannot recover) – even something from a school Warblades don’t get.
Better options include Barbarian (Lion Spirit Totem from Complete Champion can get you Pounce, and Rage is good), or Cleric (the BAB loss is a shame, but not a huge deal: Domains can get you a wide range of things, you could get some utility spells, and Travel Devotion from Complete Champion is an excellent option), or even Ranger (great BAB/skills, some feats). If your Charisma is good, Knight might be OK (d12 HD, mostly, though, since you won’t get Bulwark of Defense at Knight 4), and if you can retrain one of those Fighter levels, Paladin’s Divine Grace is pretty awesome.
Replacing Fighter with Warblade
This is mostly about taking maneuvers that replicate your feats. I’ll just go down the list:
Skills
You have 2 more skill points per level now. I recommend Concentration for one because Diamond Mind is an excellent discipline and relies on it heavily. The other can be whatever you like.
Power Attack
This is probably a feat you should still take as a Warblade.
Cleave and Great Cleave
There are maneuvers that have similar effects as these, from White Raven or Iron Heart.
Improved Critical
How do you have this? It requires BAB +8. Anyway, it’s not a very good feat, and is unlikely to change much about your character if he doesn’t have it (which is why it’s not a very good feat).
To replicate the idea that your warrior is good at that perfect strike that does extra damage, take a look at the Diamond Mind discipline. It’s all about having that perfect strike.
If you really want to focus on critical hits, take blood in the water (Tiger Claw stance), and probably just take Improved Critical as a feat, or make a keen weapon, or buy a scabbard of keen edges.
Toughness
A Warblade’s HD is a d12 to the Fighter’s d10; that’s an average of 1 HP more per level, and 2 at 1st level. Thus, a Warblade 2 without Toughness has exactly the same average HP as a Fighter 2 with Toughness. After 2nd level, this continues to favor the Warblade unless the Fighter continues to burn feats on Toughness (which is a terrible idea; Toughness is an awful feat).
If you really want to spend a feat on your HP, take Stone Power; it’s very, very good. Temporary HP that you can refresh every round can take a lot of HP off that which is actually hitting you over the course of a day.
Recommended Low-level Warblade Maneuvers
Take moment of perfect mind (Diamond Mind counter); between maxed Concentration ranks and a good Con score, it’s almost a free pass on one Will save per combat (more if you recover it). The Reflex and Fortitude save versions aren’t nearly as important because Fortitude’s your good save, and Reflex saves tend to 1. just be damage, rather than death or worse; you have a lot of HP for a reason, and 2. tends to deal half that damage even when you do save.
Take mountain hammer (Stone Dragon strike) when you can: in addition to being a great attack, it’s the Initiator Swiss Army Knife. It ignores Hardness, which means you can mountain hammer your way through almost anything given enough time. Better than an adamantine pickaxe.
Punishing stance (Iron Heart stance) is probably the best stance available to you among the 1st-level stances. The aforementioned blood in the water (Tiger Claw stance) is not bad, either, though you really have to build for it. Hunter’s stance (Tiger Claw stance) is a good second stance, since it gives you some utility. Taking a Tiger Claw stance also allows you to take sudden leap (Tiger Claw boost), which is a great choice (that requires that you know another Tiger Claw maneuver).
Otherwise, pick two or three disciplines to focus on, and take the maneuvers that sound cool. Iron Heart and Diamond Mind come highly recommended, and White Raven does as well if you’ve got other melee types in the party. Tiger Claw is very good as well; Stone Dragon has some powerful effects but it does tend to lag behind the others, particularly if you enforce the requirement that they be initiated while standing on the ground.
Troublesome Maneuvers
You should consider iron heart surge and white raven tactics. These are both 3rd-level maneuvers (a bit out of your reach at this point), but they have to be mentioned. They’re the two most problematic maneuvers in the book, but they’re also very good, even ignoring the stupid abuses that their poor wording can cause.
Iron heart surge is extremely vague in how it works, and due to some poor wording in the book and some really poor interpretation in a Customer Service answer, it can do a lot of things it probably shouldn’t (like arguably shutting off the sun...) and can’t do a lot of things it probably should (like throwing off mind control). It’s a great maneuver as long as you and your DM agree on what it does or doesn’t work on. Mostly, if you can imagine Conan shouting “By Crom!” and getting out of it, iron heart surge should work on it. That’s basically what the maneuver is.
White raven tactics is very powerful. It’s broken, however, if you allow it to be used on yourself (which, by strict RAW, it can be since you count as your own ally). Just clear it with your DM before you take it; if he’s aware of the shenanigans it can get up to, he may not appreciate seeing it on your sheet without a talk first. I do not recommend using it on yourself in most campaigns.
I’m going to answer “how do I combine Dervish with Lightning Maces,” rather than specifically how to get a slashing mace.
Aptitude Special Ability
The aptitude special ability from Tome of Battle can be applied to a weapon to cause feats that are specifically for another weapon to apply to the weapon with aptitude. It is likely that the designers meant just to let you switch Weapon Focus (dagger) to your aptitude longsword and similar, but the wording of the feat allows even feats where you never had a choice about the weapon type to apply to the aptitude weapon. This is frequently quite powerful, and occasionally completely nonsensical.
If you really want to use maces specifically, you could have an aptitude light mace, and then apply the Versatile Unarmed Strike feat to it. This is probably going to fall into the latter category for most groups, but it’s RAW-legal.
Alternatively, you could use an aptitude slashing weapon, ideally one with a large threat range (the kukri is almost certainly your best bet here: light slashing weapon with a large threat range), and then let Lightning Maces apply to it.
In either case, the Roundabout Kick feat works similarly to Lightning Maces, but for unarmed strikes: once again, aptitude can allow you to take the extra attack with your mace or kukri.
Combined with Disciple of Dispater, the kukris are looking at enormous threat ranges, which means you’ll score a critical on very-nearly every single attack that successfully hits. The maces are only somewhat smaller. Combined with Lightning Maces and Roundabout Kick, every critical triggers two attacks. Your number of attacks is thus more likely to increase rather than decrease; if you hit on the first two or three, you are statistically unlikely to stop attacking until the target is dead.
This is, of course, broken.
Were I your DM, I would allow you to have your slashing mace or allow Dervish to use non-slashing weapons without a second thought. On the other hand, Lightning Maces already is on my banlist. I also consider any combination of aptitude with a feat that couldn’t normally select the weapon in question to be something to be adjudicated by me, on a case-by-case basis.
Best Answer
No, there is no hard limit.
I can’t really cite any rules on this, other than to say that I am quite confident that no one will ever be able to cite a rule that enforces any such limit.
Of course, you’re unlikely to get too many extra attacks from that set up. Maces do not have wide critical threat ranges, and every crit just gives you one more attack so you only keep attacking as long as you keep critting (which you’re unlikely to do). Blood in the Water helps you hit (and therefore confirm critical hits) but it doesn’t help you actually threaten a critical in the first place.
Now, if those were +1 keen aptitude kukris and you had the Roundabout Kick feat, and you took levels in the Disciple of Dispater class, then you’d be looking at a reasonably high likelihood of literally unending attacks. Because you have both Lightning Maces and Roundabout Kick, and aptitude makes those both apply to your already-wide-threat-range kukris, and Disciple of Dispater is a 3.0 prestige class that (in keeping with the way 3.0 worked) expands your threat range in a way that stacks with Improved Critical or keen, well. You’d score a critical threat on most rolls that hit, confirm that on most rolls, and every time you did you’d get two extra attacks. All you need is to crit a few times in a row (not unlikely for you) to give yourself a fairly enormous pool of attacks, that is more likely to expand than it is to shrink.
And if you can find a DM who will let you run that, more power to you. For what it’s worth, Lightning Maces was banned in Test of Spite, which was a very high power arena game played on Giant in the Playground.