These are who I would like to see the Bucks target during free agency. They have limited flexibility as they're likely only able to use the taxpayers mle.
Priorities should be keeping Lopez and Carter, assuming Middleton doesn't opt out. If he does then the entire plan probably changes. It opens up the possibilities of a sign and trade as they may not get hard capped. It also opens up potential of more cap flexibility.
Assuming Middleton takes his player option I think the Bucks should be looking at some more youthful options such as Brissett who can contribute but won't cost a lot. Other options I could see are Dario Saric, Aaron Holiday, Yuta Watanabe, Shake Milton, Hamidou Diallo.
They'll need to fill in some veteran presence as well. Justin Holiday and Rose could fill that role. Others to consider here would be Cory Jo, Seth Curry and Jeff Green.