Hickory: It's been done in mods, but only in a 'replace kit A with kit B' sense, due to hard coding limitations. Still, paying such a high price just for mostly useless kits is senseless. HoW and TotL are included in GOG release, and everything else (except cross platform) can be done through mods, including items, Unfinished Business etc.
Jonesy89: Oh I don't know, a lot of those kits could come in handy. Some might be more effective than others, but I can't think of any that are truly flat out useless.
How about like half of them?
Look at the blade bard kit. It sacrifices some bard abilities for some extra fighting abilities. Essentially it mixes the fighter and bard class but does both poorly. Better to take a character that plays on it's strengths
How about the jester? Enchantment magic was of limited use in IWD because most of your enemies were undead. That charm song thing they have is only going to be useful at certain parts of the game.
The Totemic Druid is gimmicky at best as they only have summons, something regular druids and mages can do anyways. Summons are good but when comparing 1 casting/day every 5 levels to the number of available wizard spell slots, it's just kinda dumb. Beastmaster have the same problem but with very hefty weapon restrictions. Not only that, but summons weren't needed in every area, no point in these characters.
How about the avenger druid? -2 to str and con for a few spells the wizard can have? How much more pointless can a character kit get?
The Cavalier is also pretty shizzy. +3 to dmg and to hit against draconic and demonic creatures? How many of these are in IWD? You have the end bosses in the OC and HOW, a few summoned glabrezu in TOTLM and the cornugons if you put the wrong stone in the wrong slot in the portal in a final part of TOTLM. That's it!!! If wyverns count at draconic creatures, fine, they're are a few to kill in the first area of TOTLM.
Inquisitor is also pure garbage. This guy's main focus is dispel magic, which can be handled by a cleric because clerics in IWD don't have many great 3rd level spells anyways. I also didn't need many castings of dispel magic either
The stalker ranger kit also blows. You can't back stab the undead which IWD is loaded with and back stabbing in IWD isn't really a good idea anyways because the areas are just crawling with monsters. Hit one guy for hefty damage and all his friends and family gang up on you. Because of this, the assassin is also crap.
There's more, but I think I made my point :)