IF he has no future as a QB at the next level and IF he has no plans to change positions to possibly have a future in the NFL, then he probably has to cash in now and his main priority may be making as much money as he can before his football career is over.
And on another note, if he were willing to consider a position change for an NFL future, what would that be? He's too short to be a tight end. RB, WR, DB? Is FB even a thing anymore? I know that Michael Robinson made the switch from college QB to NFL FB, but I'm not sure how many teams even use an actual FB anymore, seems like that role is filled by a TE these days.
that's a lot of ifs, but why not play.
IF the goal is to maximize total lifetime earnings related to football, I'd advise him to do everything possible to protect/enhance his draft status, even IF he were to be a total bust and never play a down as a QB in the NFL.
Why?
Right now, his draft projections are all over the place. He's got a broader spread of opinions and evals than anyone I can remember - the higher rated ones rate him on what the potential could be, the others are based more on what he's actually shown so far. I saw a site that did like on3 does with consensus rankings but can't find it now, and it had him averaged out as 32nd rated player and borderline 1st/2nd round with the spread being into the top 10 down to the low 3rd. IF that were to hold at least at the top of the second, that first contract is worth $9M+, and that's life changing money for him and his family, especially if it's invested well. It's a bet worth placing that unless he loses the starting job this season that an NFL team would take a chance on the potential, even if he doesn't really progress on all the things he needs to do to be an effective distributor. Face it, Anthony Richardson put up very sub-par stats as a QB in the SEC (not as good as JM last year), but was still drafted top 5 based on potential and even started the NFL season before being lost for the season due to multiple injuries sustained and only playing 4 games. So do EVERYTHING under your control to at least get that first contract at least toward the top of the 2nd. That contract value dwarfs anything you can get now.
On other positions - it's way to late for him to make a change and have any real expectation of holding onto a first or early second round pick.
But, hypothetically, what could he play? who knows. He certainly has measurables to play RB or Safety. Maybe LB but that's a stretch without a few more pounds. WR, specifically slot, could be an option also. Thing is all those positions have intangibles also, and without seeing a guy take reps at those spots it's hard to know. For example as a S, a player has to have a certain degree of hip flexibility and mobility - not to the same degree as a CB, but more than a QB needs to have. Does JM have that trait? He might, but we just don't know because we've not seen him in a position where he'd have to show that.