Celtics
Simons could be a bench piece for the future. He is efficient and young. Schroder will be gone next year anyway and the Celtics can still make a bigger splash this coming off-season, owning all draft picks after this coming draft.
Blazers
Get that 3rd star player to pair with Dame + CJ. He is a good defender as well, so they don't miss much on that end losing Covington.
Pistons
I wonder if Grant is worth more than this. 2 first rounders, 3 second rounders, and an expiring contract: is that enough for Grant? I'm not sure.
Clips
Get a solid back-up PG for a title run when Kawhi returns. I wonder if Schroder would fetch 2 second rounders. He may not be worth that much to a team, as he is a one year rental for a team like the Clips.
Overall
Pistons and Clips might say no, while being more required from the C's and Blazers. Honestly, it's hard to gauge Simons trade value alone, (the reason for me trying to construct this trade), because he's always part of a larger package and I don't think I've ever seen him traded by himself.