How would you fill 2+ more seasons?

I'm not asking for your theories about monsters or Fromville. If you were in the writing room and asked to draft season 4 AND 5, what would you do to keep it interesting?

I think that wrapping up the major plot points and mysteries would take, at best, 4 episodes. That would leave about a season and a half to be filled.

I'm not a fan of flashback episodes, so I can think of a couple of things to keep it intriguing. a) the Frompeople find other inhabitants of the same space. It was done in Lost and overdone in the Walking Dead. Or B) some main character manages to escape Fromville and, unlike Tabitha, tries many things to help those left behind.