Lots of possibilities. In fact they may not be individuals at all, but rather a symbolic representation of the Word of God; "law and prophets", or OT and NT. Or perhaps the twin witness of believing Jews and gentiles together in Christ's church.
I remembered this in support of your argument that everyone gets to croak at least once. Even those two, IMO.
"Why not Moses or Jeremiah, John the Baptist or Paul?"
They all already died once.
"Or someone not yet born?"
That is quite possible.
"Lots of possibilities."
Yup. I'll still go with Enoch and Elijah though.