I don't think the movement system is going to change to allow multiple characters to be selected. The way it is now, it is extremely "controller friendly" and since controller support is going to be added, I doubt they are going to create an entirely new movement system that will be completely separate from the controller based one and only work with mouse and keyboard. The movement system is also very "multiplayer friendly."
That said, I think there are some more simple things that can be changed to make it much less frustrating.
1. If you press "c" or click the stealth thing, just make every character currently linked to the one you are controlling go into stealth or come out of stealth.
2. Provide a way for party members to teleport to one another. Do it just like the pyramids in Divinity. This will solve the issue of one character jumping over something and then having to manually jump every other character to them.
