Which is exactly what I am afraid of. I don't think the game will be fun for me if that happens. AI will just stick themselves into a coalition against me, and I have to fight all of them for each province.
The only way this is not going to be a clusterfuck is if I can make separate peace wiith each coalition member in order to take something from each war participant.
I see your point, but I think you're forgetting to include that AI coalition members will no longer be able to say the war leader can't negotiate for them. As long as you build up quality vassals with strong militaries of their own instead of using them as province containers, it would actually make coalition wars a lot more fun and rewarding, since it'll be more "you and your dudes against your target and their dudes" rather than "you against everyone whose territory you want to seize." I have an Ottomans game going where I've built up 8 strong vassals, and I'm definitely going to have to return to that game in ~1650-1700 or so and have a big ol' world war with all of continental Europe after the patch. I'm pretty sure I can actually seize Europe faster if I don't have to work with the current war negotiation bug.