Ooh, that would be interesting to see. ovo Though yeah, I guess that would involve either a nearly complete swap of characters in some cases, or, as you said, time travel. :'DD
I actually realized _after_ I created Thalia that I would have liked to have made a character on the opposing side that would have to be recruited over. Classic FE technique, after all @ lord speaking to the single unit on the enemy side who has a pretty/unique sprite. :'D