Problem with any trade for McCarty talk is MIN has zero reason to trade him, unless they don't believe he can actually be the guy.
First at the end of the day only MIN knows how much is real and how much is smoke and mirrors with Darnold this year. For the sake of discussion we'll just go with it's mostly real. It is still only one year of production. Investing the going QB contract price is not something you do with so much bad production vs one excellent year of production.
Lets say you could sign him at the going rate, but on a 3-4 year that allows you to get out of it after 2 or 3 years. You got rid of the guy you believe can be that guy for a draft pick. You're right back where you were, but actually worse off.
MIN can franchise Darnold, see if it was a one year wonder or if he truly is the long term answer. With JJ on the roster you get more time to evaluate him (double check you're belief he can be the guy) and if Darnold was a one year wonder you have JJ.
Darnold really has become the guy you lock him up after 2025, and then you move JJ.