I like these a lot. And by and large they all seem quite nicely balanced against existing feats; they give more options than some feats that may be considered weak, but without being so compelling that nobody would ever take the original feat any more.

Except maybe Battlefield Agility, which overcomes Spring Attack's main flaw: it's strictly less useful than equivalents like Fly-by Attack. Since it's such an improvement, the Tumble 8 ranks prerequisite is a good idea but might be a bit low. (On the other hand, Spring Attack avoids AoOs...)

Battle Casting looks interesting, but can't you already make AoOs with a held touch spell?

Love Channel Ki.

Combat Flair seems like possibly the most powerful of these feats, since it's an extra bonus rather than replacing one ability score with another. But it can afford to be, since it gives Charisma a good use and only applies to certain underused combat manoeuvres.

I don't really "get" the flavour of Combat Instincts, but it's definitely a clever idea.

Crack Shot is a really good idea. It's obsoleted by Improved Precise Shot, for those who qualify at higher levels; but I guess anyone who takes that feat could retrain or otherwise negotiate replacing Crack Shot with Point Blank Shot.

I'm a bit dubious about the Mounted Defense feat... let's see, it's "whenever" rather than "once per round", but only usable against "an attack roll that wouldn’t have hit you", and you rather than your mount take the hit if you fail. That last part would make a good feat by itself, I think; the "whenever" part throws my sense of balance into a spin (how does this affect it? is it better? but it means you might take a lot more attacks!), while the "wouldn’t have hit you" part just seems to add complexity.

Reckless Attack has the wrong descriptive text.