I love this hypothetical.
In a vacuum, there's a wide variety of players we could get. You could argue that because of showing actual big-league success, each of these guys is more valuable than a prospect in the 15-50 range. (maybe even 5-30). There might be two or three actually untouchable players, even for three top 50 prospects. Ohtani, Witt, Judge, Skenes. Those four are the face of MLB right now. I'd have to think anyone else in MLB could be moved for that trio.
In reality, there are other factors like payroll flexibility, available free agents next winter, a team being large or small market, individual team strengths, blocked prospects, etc. that would probably cross a few more players off the list.