the way i imagined this scenario working, btw, was that i'd get to go back in time and visit the dead ones while they were still alive, not that they'd be ripped into the present, or some sort of inter-temporal messaging system
so i guess, what i'm saying is, i also wouldn't mind getting to briefly be a tourist in early 20th century paris or yuan dynasty china. if that's not part of the scenario, i may rethink.
otoh, completely divorcing historical personages from their historical settings seems difficult.