The obvious suspects would be the former Budenholzer guys: Millsap, Jeff Teague, and Kent Bazemore. They're also reportedly targeting Avery Bradley. Justin Holiday would make sense considering we just got his brother.
I would imagine the Bucks will at least give Goran Dragic a call to see if he'd be willing to take less money to play with Giannis and Bogdanovic, but I doubt it. Likewise with Danilo Gallinari and Jae Crowder.
Some guys I would personally look at:
PG: Jevon Carter, Reggie Jackson, Shaq Harrison, Kris Dunn, maybe even MCW if you still consider him a PG
Wing: Bazemore, KCP, Justin Holiday, Denzel Valentine, Alec Burks, Josh Jackson, Derrick Jones, and there's always the option of trying to bring back the guys from last year (Matthews, Connaughton, and Sterling Brown).
Big: Nerlens Noel, Derrick Favors, Aron Baynes, Millsap, Harry Giles