Would it be possible to basically restart the timeline, start recruitment again, but keep the characters of remaining players?

I think with an RP this large in scope we either need a lot more players than currently seem to still be here or a lot of NPCs. We could just NPC the characters that have disappeared, but I think it would be more interesting to have RL players instead. Of course, I can't speak for other people's preferences, and this is your role play, so whichever you and everyone else prefer...