Is there absolutely ANY indication on where a Xaela might start, or what class?

[Hinoto-no-Ryuji]

Thanks Ryuji!

Also, as far as "changing my mind later", I just mean that I've already leveled two characters up to about 30, so worse comes to worse, I can always just level up my Ul'dah/Immortal Flame character.

Anyways... I suppose we don't really know anything about Othard yet, either?

We don't know a lot, but we also don't know nothing! Here's what we know so far:

-Its (native) population is at least Auri and Hyuran.
-Geographically, it is mountainous in the East; this is where the Raen come from. The western reaches of the continent are a "vast steppe" (basically, a grassland or prairie); this is where the Xaela come from. There is also a small set of islands to the East that may be home to a third type of Au Ra.*
-It has been completely conquered and subjugated by the Garlean Empire, a process which began a couple decades or so before the Calamity. This was achieved at great loss to the Empire, since it was the first place that they encountered Primal summoning (and that, in turn, is the reason they're so hell-bent on strangling Eorzea's ability to summon before committing to another large offensive). The effect of this war and the current occupation on Othardian culture has yet to be detailed. You can read a little bit more about all that here.
-We know that it holds (or held) the cities** Doma, Rabanastre, and Dalmasca. Those last two have been name-dropped in the Japanese version only; their presence in Othard was confirmed in an interview with GamerEscape. Doma is (or was) in the east, likely in the same region as the Raen; nothing is known about the other two. Doma was "razed" when they took advantage of an Imperial war of succession to stage a rebellion; this means it may not actually exist at all anymore.

And...that's about it, really! I'm sure somebody will let me know if I missed something.
___________________________________________________________________________________________________________________________________
*I could have sworn this was discussed in the Kagoshima lore thread, but couldn't find the details there, and haven't been able to find the actual source for the life of me. But I definitely recall this fact being brought to light recently.
**I don't think the exact nature of Doma has ever actually been stated, and there's a lot that implies it's a region (ala La Noscea or Thanalan) rather than a singular city or city-state. Most of that implication comes, once again, from the naming conventions post, which regularly refers to Raen conventions as being Doman, which to me makes "Doman" sound like it covers more than just a city. That's just a theory, though, and has no backing in-game one way or the other.

[Rosenoire]

As other folks have said, you may be approaching this backwards. Maybe try deciding what your character is like, and then work the backstory out from that direction.

I fantasia'ed my WoL from his previous incarnation as a Duskwight Elezen. I prefer playing casters, so I wanted to keep his starting class of Arcanist. I thought about having him be from the tribe that uses chess to determine leadership, but I liked the idea of someone from a coastal, seafaring tribe ending up in Limsa. Start with what you want your character to be, and go from there.