This has been requested by a lot of people, so in the future, when adding new scenes to existing enemies, I'd like to be able to do something along these lines.
I was considering either a special Game Over with a specific enemy, or as you've suggested here, inviting them to your Safe House as a temporary (or permanent, if you really like them) guest.
The only issue with having a proper 'guest' system is having to whip up map sprites for each enemy involved. Some would be easy to do in engine, but some of the more out-there enemies would require custom sprites, which take a lot of time.