We had that. It wasn't a limited job, but it was called Astrologian. Still in the game, but it just doesn't have haste, stop/slow and Disable like it used to. Astrologian is still a healer with rewind and space time magic. It's built on regens, and it's big heal, MacroCosmos is legit rewinding time to heal you based on the damage hp loss during the duration. It used to have Extend, haste for others (except just the caster, and a bunch of other things.). And it still has Gravity and space magic for offense. Delayed heals and everything.

I highly doubt they'd just make another job called Time Mage. Because, AST still has that class identity, of space and time healer, however stripped of what it used to be. The only thing missing is the Sugarloaf hat, which you can get in ARR. Dye it red and wear some white or blue dyed robes.