Before we get into speculation - I really wish they would let Ray use some future-tech upgrades to take the ATOM suit out of "Iron Man knockoff" territory. Nanotech or whatever.
Just some random suggestions for characters who could appear, or turn into semi -regulars or even spend a season on the show at some point:

sort of borrow from 12 Monkeys or Continuum if the writing was up to the task. I could see it.

the irony is that while the last thing they need is another reboot, the only way to do it right is to toss out everything (or at a minimum, everything since '86) and start fresh.

I think that's a good take - which is why I never understood the hostility towards the Waid/Kiston run, it struck me as a (to borrow your analogy) DS9 take on the Legion which I liked, both artistically and characterization wise.