Why would recruitment centers, scout guilds, temples, and shrines matter to determine how the nearby regions' people think of that region/realm? They aren't exactly there to serve the peasants (unless they are of the specific religion those temples and shrines belong to, in which case you can use its levels instead).
Aside from that, though, pretty much everything you mention either is the case now or has been at some time in the not-too-distant past (regions revolting to other realms from rogue is not, I think, currently possible, but it was a few years ago). It mostly frustrated players when regions would join realms apparently at random like that. I can recall hearing of maybe one or two cases where the equivalent of your Realm 3 actually tried to keep their Region D and play politics around it; mostly, they either just willingly gave it up, or got war declared on them by at least one side in the pre-existing conflict before they could even take a position.
