I was subliminally rooting for Cupp to be a possibility, knowing it was both a longshot and also probably too risky to mess with. But the expected price was starting to look right. Stefon Diggs is probably a better but still not that likely a possibility. He may get caught up in the drying up market and have to find a team, and the Cowboys might be there waiting. Amari is a flat out no, and I wouldn't expect either side should really have mutual interest.
I think a WR like Tyler Boyd would make a lot of sense for the Cowboys. He's been a pretty productive and dependable number 2B or 3 type receiver for years, he's cheap, nobody's talking about him. he would probably be a clear number 2 WR for Dallas, and probably an upgrade over Cook. Can't really blame him for being stuck in a total dumpsterfire offense last season with the Titans.
A guy like Keenan Allan my be a possibility, at least would be a good veteran presence, not sure how much he las left in the tank. I could maybe see Tyler Lockett happening, but not really sure he's the type they really need. If you want a smaller dink type Elijah Moore would probably be a better value.