Bryant is likely going to have two years of control because don't see him winning the grievance absent some evidence we don't know about. Cubs figure to be a legit contender for both those seasons.
With two years, makes no sense to me to trade him for an average regular and a back-end top 100 prospect. If one year of control (like Betts), that would be different, maybe.
It's not like Indians and Lindor. Indians have basically zero chance to re-sign him when he hits free agency in two years. Cubs can make a competitive offer to keep Bryant in two years. In the meantime, hard to see merits of weakening club in short-run for those two seasons when you're trying to win the WS.
Would also be different if you could get a return of a plus major league ready guy(s) now for Bryant and fill 3B with another good player, either by trade or free agency, and gain some years of control in the Bryant package. In the end, hard to evaluate without seeing who the actual players may be.