I think that AEWs roster is bloated as it is, and shouldn't really take on more ex-WWE guys, but if I was a scout...
Out of all of the releases, I'd pick who most would pick, Keith Lee, who, as proven by his NXT run, can have bangers. Mia Yim isn't half as good, but can she talk?
That's the same with Killer Kross and Scarlett Bordeaux, though they both impressed me more in TNA than WWE. Kross has a great look and can go in the ring, yet he shouldn't be on the mic too much, and Bordeaux was gorgeous, charismatic and pure sex, but she looked rough in NXT. They need to do away with the overly elaborate theme too.
I'd like to see Harry Smith in AEW, perhaps as a part of Team Taz. Do away with the bulldog and the Union Jack stuff though. He isn't British. It's cringeworthy. He needs to be his own man and not play so much into his father's legacy.
Taya/Franky Monet has a lot of personality and is good in the ring.
Ember Moon? I'd like to see her on Dark and be rebuilt, though I wonder about her injuries. I wouldn't build a division around her, feel the same way about Ruby Soho.
Gran Metalik and Lince Dorado? I'm not a big fan of Luchas, but maybe they can do something with the Lucha Brothers and see where it goes from there. I can see those matches being spectacular.
Out of all of them? Honestly, Keith Lee is a no-brainer, but I'd also pick Harry Smith in an enforcer-type role. The rest of the above would be fun and have potential, but I'm not itching to see them.
I don't want to see her on AEW, but I'm curious to see what happens to Nia Jax. With two bum knees, I've got a feeling that's it for her.