It does sound fun and I have seen some community appeal in the form of requests for my spellcrafts mod, where a couple users saw I left in some outsider-controllable megabeasts I was testing and wanted to expand on their capabilities or make them play nice with townsfolk at least some of the time. Mechanically I imagine if this was intentionally implemented it would just be a playstyle in adventure mode, where because you're playing as a megabeast you get kicked out of towns (as is currently the case; everyone aggros you as a megabeast or night creature, but maybe they should hold back and just tell you to leave and try to organize an actual militia or mob to force you to leave/kill you) and make friends/family with other beasts (which is not possible currently; other beasts are just as hostile as townsfolk).
Some things you can't do currently; make permanent friends/family with anybody in adventure mode, especially as a megabeast. Break down doors or other obstacles, even as a building destroyer. Expect any sort of resistance to a rampage besides the occasional peasant that chooses to fight instead of run. Or be pursued or hunted by the law or military, or bounty hunters, angry peasant militias etc.
It can be fun to run in and slaughter entire populations, but there's no rewarding game mechanics or escalation as a result currently.