So with the change that the warleader can change who occupies a province, it presents itself with an interesting, but somewhat weird, mechanic:
You can, once again, 'feed' vassals. Beyond that, you can even cause massive overextension by giving some minor country huge swathes of uncored land!
Proposed solution:
Allow anyone gaining land in a peace deal to deny the proposal. This way, you can set up the AI to decline any peace deal which gives them huge amounts of overextension, or, for example, bits of land which they can't core. In general, anything nonsensical.
You can, once again, 'feed' vassals. Beyond that, you can even cause massive overextension by giving some minor country huge swathes of uncored land!
Proposed solution:
Allow anyone gaining land in a peace deal to deny the proposal. This way, you can set up the AI to decline any peace deal which gives them huge amounts of overextension, or, for example, bits of land which they can't core. In general, anything nonsensical.