If I were chasing a Bucks free agent, it would be Lopez or Middleton.
I've always liked Middleton and advocated trading for him a few years ago when that was a possible thing.
That said, I think at this point, we already have three very nice top quality wings in Hayward, Brown & Tatum. We don't need yet more positional redundancy at that spot. We can definitely field three of those guys at a time in a starting lineup. But going 4-wings might be a bit of a stretch.
Lopez would fit -- we obviously have a need for a big man.
But I personally would like to try to steal Brogdon. I think Brogdon is a near ideal match for what this roster and Brad's system calls for in a PG. He's not at all ball-dominant, as he's worked very comfortably off-the-ball with Giannis as facilitator and so should be able to work fine in a lineup that featured Hayward as the primary playmaker. Yet he is also comfortable and competent as the primary ball-handler. The ability to move smoothly between both modes is what Rozier struggled with. He's an incredible marksman who really commands attention on the floor even when off the ball. And he is a good defender with plus size for a PG.
To me, a lineup of: Brogdon+Jaylen+Gordon+Jayson+<quality big man> would be very, very effective on both ends of the floor.
This last year, the trio of "Jaylen+Gordon+Jayson" played a couple hundred minutes with non-Kyrie PG (i.e., Rozier or Smart) and non-Al C (mostly Theis and a little Baynes) and was incredibly effective. Heck, the Rozier+3-wings+Theis lineup was over +19 Net Rating.
I would make an aggressive offer sheet for Brogdon that clearly would push MIL into the luxury tax should they try to match. If they match it, fine. At least you've made them pay through the nose. And maybe that forces them to let go of one of their other FAs.