If not for the untradeable contract, i could ALMOST see this being feasible. Teams reach and overdraft QB's almost every year.
I know its not 100% on him, but Murray only has 1 winning season in 5 years. The last 3 years his games played have decreased. He's a smaller QB that loves to run, maybe this is a precursor to what his health is going to look like in the future, maybe not. I havent seen all his games, but i do think i remember him having some **** luck with WR's that loved dropping the ball.
One other thing to think about, if Murrays ego cant coexist with Gannon, then who's to say that Murray doesn't get Gannon a one way trip to being fired. Plus another season like Murrays current and his value is going to be even less. You can probably still sell the Vikes on the fact he's worth the late first. He misses 8 games again this season and puts up similiar numbers than his trade stock is going to drop even more.
So where as i know Tannebum is a joke, this is actually not a bad idea....except for the fact that AZ would have to eat a lot of dead cap. Murray has a great arm. being in the pocket isnt his game, but if you could convince him to stay in the pocket a little more than he would probably feast with Jefferson. I do think with all the cap that Az is going to eat, then i want a little bit more than #23 though. And more than likely McCarthy is going to get overdrafted anyways because he has the "looks" of a prototypical qb.
If you are AZ though, you have to do this on draft day. Would backfire big time if you made this trade today and then the Pats pick JJ at #3