Though this would be quite an interesting experience. Not super hardcore, but certainly would alter most ppl's play style.
No fighters allow in party (not even multi/dual classes)
No ranger, paladins, or even monks.
This removes a good chunk of our "go-to" npcs in the game, and party composition becomes much trickier.
I'd probably start by slapping armors on a bard and/or priest to serve as tanks, while the rest sling/dart/bow on. At higher level fights will most likely be spell-focused battles! How fun is that?
This challenge can potentially apply to both BG1 & 2, though I cam up with this with BGEE in mind.
Have fun and feedback appreciated!