This is one of those things that, at the end of the day, is
very contextual. Are the peace deals being
negotiated, or are they being
imposed? If you're imposing your conquests you don't really give a damn about whether or not you're carving out exclaves; you're taking everything you could get your hands on. If you're negotiating, you're not gonna wanna be left with a chunk of territory that cannot be accessed.
You know how I mentioned the idea of "codified borders" in the
suggestion thread I made on raiding? Here's a broader idea: peace deals aren't peace deals. They're establishing the reality of your conquests. Carve out all the exclaves that you want.
However, until you actually sit down and
negotiate a formal settlement (through a generic action and... god knows what sort of fancy UIs and all the rest of it I can drum up for this), you're still "in conflict" even after peace. Stuff about exclaves and all the rest of it only get handled during that negotiation process.
That way you get your "bilateral peace", but
after the war ends, and as a protracted negotiation that can possibly take years. These are the peace treaties that do things like clean up borders and the like. Until you've actually had that negotiation, you can do things like cross-border raid and the like. Note that you can even be allies with someone, or have them as a subject, without formalized borders. Won't be able to raid, but the stuff I mentioned in the
authority thread about lowered control in locations adjacent to foreign territory without codified borders still apply even with your allies.
No-CB wars? Ding your stability a whole lot more when declared on someone whose borders you've formalized. Much cheaper against someone you're already effectively in a state of conflict with.
Consider this a refinement on my
previous idea.