As far as people he didn't ever record with, it's hard for me to say. I think a session with Getz and Haig early 50s would be beautiful. I also think he would have done very nicely with Coleman Hawkins. A shame, too, that George Russell never arranged a group for him.
As far as people I wish he recorded with a lot more: Lee Konitz, Lucky Thompson, Al Cohn, Kenny Clarke, Horace Silver, and of course Bill Evans. And lord would it have been great to hear him accompany Billie in a small group, but the timelines just don't jibe; she was too far gone by the time Miles came into his own Of course, my post mostly revolves around his Prestige period. Sorry.