Pretty much all there in the title.  I should say that this occurred to me while I was being a cheese-monkey and running circles around a random monster with my newly matured daughter, because I really didn't feel like waiting 15 months (weeks, years?  who knows what time scale turns are on) outside of combat before she could summon her second elemental.  It seems silly that I've got units who are able to recover from the most terrible wounds in mere minutes as long as they're fighting something, but revert to being bedridden as soon as they're at peace again.

Logically, any creature with any sort of per combat turn regeneration should be fully healed after a single map turn, but obviously that presents balance issues.  I think simply adding their combat regen to the normal non-combat regen and allowing it to function outside of friendly territory would be fine.