I'd happily see us sign Hamza and Holding. Both of them have shown their PL qualities, even Holding in his limited game time has proven himself to be far too good for the Championship.
Robinson has to go. He's an upper L1 CB at best, and keeping him would be nothing other than negligent.
I wouldn't be disappointed to see Brewster get a new deal, on significantly reduced terms. But that would largely depend on how we are likely to set up tactically next season - we shouldn't sign him to play as a striker, but he's done a solid job in a wider role, particularly in the 2nd half of the season.
Diaz has been a complete waste of time. He's admittedly scored a couple, but he's not done anything that couldn't have been done by anyone else. And then he's out injured for weeks, gets brought on yesterday, and in the brief time he was on the pitch he did fuck all.
Gilchrist and JRS, we've seen glimpses of quality from, but they aren't players I'm eager to see back. Resources can be spent elsewhere to greater success I think. Same for Clarke too, though I might feel different if he'd played more.
If we could sort a deal for Souttar once he's completed rehab for his injury, I'd take him back in a heartbeat.