I think it might be easier to have them summoned just so we can get all our main characters together for convenience unless someone would like to introduce their character later that's perfectly fine
Ehhhh, I'm not opposed to the idea. But it is a big potentially complex one one that could get hard to exicute and could go wrong as many ways as it could go right.
I personally would suggest it for a more planed out game, or a game that is already built around the idea, rather than one that's sort of a straight forward pick-up-and-go as this one is.
Especially if you have extended game place sequences in the future or alternate time line, that leaves us sort of out of it? I mean yeah out demon characters could possibly exists 100 years from now or even all the way into the modern era but that would sort of ruin the suspense on if any of our demon character's lives would be in danger wouldn't it?
IDK what are other thoughts.