I read your PM and that concept sounds fine.
Yes, still 10th level, though whomever gets the spot will acquire all of the current character's XP (minus bonus XP granted to the player for their RP) in order to keep everyone roughly at the same pace.
The build ideas sound fine. The group currently lacks a jack-of-all-trades/roguish type and an extra fighter type always welcome. This is not to say that only applications filling those slots will be considered, but all your ideas happen to fit nicely in those voids.
Any player chosen to join will be measured on their own contribution. My only requirement is that the character submitted be a male dwarf named Wurgrym. His speech patterns are all yours if you're accepted.
Swift Wing is an approved PrC, yes. Do note that there is already a divine caster type in the group though, so your application would have to be particularly good.
Do I mind..? I'm not sure what you have in mind, so I can't say if I mind. I generally frown on Min-Maxing and the other characters currently in the adventure are based on that preference, but not all min-maxing is created equal, so to speak. If you can give me a better idea of what you had in mind, I could give you a better answer...