Eh... 20k feathers is a lot to spend. If I had to pick one it'd be Eliwood (as he's amazing on cavalry teams), but I think you might be better off saving your feathers for a better red unit.
What are your other main units at the moment? Also, of the guys you listed, do any have particularly good boons?
Overall? I'm using:
Nowi
Cecilia (Who will be scrapped once I level Lucius)
and Hawkeye.
I already have Eliwood on my team, but he's noticeably bad, so i want to replace him.
I almost have Felicia and Ana ready, but not quite.
As for boons, I can't say a whole lot...
Selena: Level 1 right now...
Alfonse:
http://imgur.com/a/n7cqu (It's too early to tell, I think)
Eliwood: +HP/-ATK (AKA not that great)
Palla: Also level 1...