[Agema]

Well, bearing in mind TW is supposed to be at least partially realistic, mass slaughter of the sort from R:TW in the 18th century isn't particularly viable.

Owning Rome was quite annoying in M:TW, but then, that's something Creative Assembly should have better implemented as well. The idea as I envisage it is you'd be able to slap a treaty on a nation you defeat that effectively makes it your *****, or generally keeps it from troubling you for a LONG time, but you don't exert direct control over it. Like in Europa Universalis II: if you've got another nation well and truly by the balls, you can force virtually anything on it by treaty, and often there are better options than full annexation.