Sorry I haven't bee posting recently, but...
Why in the name of the gods would the pattern be broken though? It makes no sense to have this pattern of EoT -> 2300 -> 1000 -> 600 be broken. She's the fifth, so she should be sent to 12000 BCE. Also, her traveling through Time-Error sounds just as wacky as her traveling to the DBT. You'd need a five-dimensional Gate for that, and those do not exist in CT, otherwise you'd have Crono and Co. traveling all through Time-Error and things would get really wacky. Gates are four-dimensional punctures, not five-dimensional.
It sounds interesting in its own right, Ginger, but doesn't really hold water, I'm afraid. A reunion with Balthasar would be cool, though. (And possibly the other two Gurus...?)
I'd prefer it if she was simply an extra character you got. Maybe if you got Janus, during the Fated Hour there was a 12000 BCE quest (that thing needs an end-game quest...it doesn't have one, does it?) where the people are rebuilding the villages and there's a healer woman or something running around. If you have Janus at the end of the quest, he'll recognize she's Schala, and she joins after some scenes. You could still get something cool even if you don't have Janus, though. Perhaps getting her would enable another ending where after Lavos kicks the bucket, as a last desperate attempt, he rends a hole in dimension instead of time, and sucks Schala in. Then we're all set up for CC.
And, uh, Janus is pretty obsessed with Schala... >.> If you don't kill him and get the Epoch ending, you can see him roaming around some mountains in 12000 BCE, presumably searching for Schala. Now that he's gotten revenge, he needs a new goal to drive him, and it seems to make sense for it to be his search for Schala. (I haven't played RD and I know it's not cannon, but doesn't he come to 1020 CE in it because of Kidd-Schala? So that implies he is, in fact, searching for her)
Hm... "Holy Healing" could be toned down, maybe just make it Heal 2. Since her magic prowess is higher than Glenn's, it should heal for more. And I do agree with tushantin, there should be a barrier mage. Schala seems fitting for that, and I'm all for super-ultra-awesome bosses of doom. Why would she have Dark Matter, though? Judging from her personality, (And I'm about 99.9% sure that affinity is tied to personality) she'd be Heaven/Light.
And yes, double techs with Janus would definitely be both interesting and cool. ;) I'd be interested in seeing an Antipode-like attack, only with Shadow and Light. And, as stated earlier, Janus could perhaps make Schala's pyramid barrier seal enemies or something.
Rox gets the final say in all of this, though.