I started this Vax (alternate-universe?) story. It's just a few sentences right now.
"It is thousands of years after the apocalypse. VAX is finally wearing down, so he is searching ancient ruins for spare parts. He finds himself in the ruins of the Guardian Citadel. That is when he discovers the time-displacement equipment."
Some thoughts: By this time (thousands of years in the future), civilization could have completely recovered; the world could have entirely regrown; or there may have been multiple apocalypses since the first game.
The discovery that the Guardians held time-travel technology might mean that some of them actually escaped to the past or future, or alternate universes.
Something like this could take place after anything else that might happen in WL2. A future-VAX character could be a random encounter in WL2. You could possibly run into him early or later in the game, and he could become part of your party, or you can fight him.
I'd really like it if anyone wants to help continue the story!