Timecast acts somewhat like flashback. Most flashback spells cost extra the second time, but timecast spells put the extra cost in front, sort of like buyback. By paying the extra cost, you've assured yourself of being able to play it again. I'm not sure whether or not that's a good way to do it.

If that's the case, would it make the most sense to put Timecast at the end of the card's ability instead of the front? I got to admit, I was confused on first read because I assumed that Timecast was supposed to be doing something first, or seperate from the ability, not in addition to, after the ability is done.

There's also a bit of confusion as to whether or not you can just cast this from exile whenever it is exiled. I mean, I know you don't really have much space in the reminder text for that, and you can just clean that up in the comprehensive rules... but a person just reading the card wouldn't be able to say one way or the other. Maybe it would be better to have the card naturally exile, but you can pay a cost to stop it from exiling? Hmm.... I don't know. It solves the problem but would probably end up getting more confusing in the end.

Are you suggesting something like "If you cast this spell from your hand, exile it as it resolves. You may cast it from exile by paying \1."? In that case, it would definitely be able to be cast from exile no matter what put it there. OTOH, it would be almost the same as flashback, just with exile and graveyard switched.

The way it's currently written, it's supposed to be a pair of linked abilities that only allow you to cast it from exile if you paid the timecast cost to put it there.