I would love a mod like this!

Cause I too prefer to control just one character. I know you can kill one or leave one behind in town, but as Mr.C said, you still get the dialogue exclamation marks and on a couple of occasions I've had a 'You must gather your party' message before I could proceed.

It would be so much simpler and cleaner if you could just start with one hero from the start. I've looked into this myself, but it's way beyond my poor modding capabilities, so I really hope somebody with more skill will consider making a mod like this *fingers crossed*.