Surprised no one said Inquisitors I would love for that class to be in game .
Err... probably no one mentioned it because the Inquisitor (being a Paladin kit) is already implemented ever since BGII:SoA was first released in the year 2000.
(1) A combat dragon-disciple class. Especially if it comes with a sprite change as the character levels up and becomes more draconic!
(2) Arcane Archer (makes arrows magical, eventually firing +5 arrows and can imbue arrows with a spell, so when the arrow lands the spell takes effect)
Comments
Have fun!
http://cdn.baldursgate.com/files/baldurs-gate-mastering-melee-magic.pdf
IWDEE also adds a few more priest kits (for Tempus and Tyr) on top of what is shown there. You can find a similar manual for BG2EE here
http://www.beamdog.com/files/bg2ee/bg2eemanual2.pdf
and IWDEE here
http://www.beamdog.com/files/iwdee/iwdee_manual2.pdf
(2) Arcane Archer (makes arrows magical, eventually firing +5 arrows and can imbue arrows with a spell, so when the arrow lands the spell takes effect)
the super awesome Evil Clown - https://www.dandwiki.com/wiki/Evil_Clown_(3.5e_NPC_Class)
it'd be really neat to have at least a mini campaign against a lvl 20 evil clown. save vs 10+10+cha mod or die on sight *sudders in evil glee*
Also a few more multi-class (&dual) Options that were in the sourcebooks would be nice.
There was a way to play a Fighter/Mage/Druid IIRC.
And of course the original Thieves & Bards ability to read scrolls*, the followers of Fighters(Warriors?)...
Mud wrestler class.
Pillow fighter class
Whatcha got?
Mud wrestler class:
* fighter/mage
* Initial spells:
- Blindness (throw mud in their eyes)
- Great (muddy ground)
From there focus purely on disruptive spells. Bonus points if you decide to go kensai/mage for that unarmored mud wrestling.
* alternate: darkmoon monk (fight with your hands, lots of abilities which represent being covered in mud)
Pillow Fighter class:
* A low level monk...
* alternate: 18 cha enchantress with the spells 'friends' and 'charm person.'