The Heart of Fury approach may work for some, but others might find it silly. My understanding is that it more than triples the HP of all enemies. It also grants all enemies 5 point bonuses to both THAC0 and AC. I wouldn't want to play BG1 that way. I'd much rather have smarter AI.
I think the best approach may be to use SCS in the BG2 engine and then tweak the BG2 engine to make is as much like BG1 as possible.
You can reskin BG2 so that it looks like BG1. Serg Blackstrider may be able to help you with that.
The BG2 engine can be forced into 640 x 480 mode.
There is a BG1 walking speed mod. There may be a BG1 proficiency mod.
As for the kits, you can just refrain from using them.
I'm sure there are other angles, too.
It's not perfect -it's not what you asked for, exactly- but it may be worth a try.
Good hunting!
Best,
A.