I'm still on the fence about Time Mage as a healer, honestly.

Just like GEO with WHM, Time Mage (TIM? TMG?) is very aesthetically similar to AST, given their spells are billed as "Time and Space Magic" in Japan. AST is not only intrinsically connected to stars, but wields iconic Time Magics like Gravity, modified versions of Quick and Regen, delayed action "bomb" effects, and has only recently lost access to a couple of its time-manipulating effects (largely out of necessity due to changes to its arsenal).
I think it's more likely we'd see AST retooled to be essentially another name for Time Mage (with cards as substitutes for buffs like Haste, since Yoshi-P has been adamant about not adding that) than to see Time Mage be added as an additional healer.

Though admittedly Time Mage does sound like an interesting opportunity for a DoT Caster, particularly if it could mean retooling SMN away from DoTs and more towards pets and actual summoning. Just food for thought.