To be honest? There's not really one.
The only reason I can see, and it's probably the one that Coach Rhoads is using to justify is this: Firing a coordinator midseason and installing a new one will absolutely make the offense more inept. You can't learn an entire new system in a week. Say we fire him after the Iowa game. We have 2 weeks to prepare for Tulsa. We can install a playbook--at least part of one-- and it will work against Tulsa, because they haven't seen any it.
But when Texas watches the film from the Tulsa game, they're going to see that we only had 20 plays to call that the offense could run effectively. So they prepare for those 20 plays. Say we get another 10 installed and working well before the Texas game, great. So Texas can effectively stop 2/3rd of our playbook with no trouble.
I mean, it's a start. And by the end of the year, the offense should be functional, but it just would not be a smooth transition in season, IMO. Even though we have other coaches on staff with experience, hiring them to run the same system as Mess doesn't solve a damn thing--the offense would be just as inept. They would have to run a different system. And sure, maybe we put in "elements" of the Pistol this season, but to completely change from to it mid season would not have any better results.
I'm still of the opinion that we should fire Mess. Just bite the bullet and say **** it. We are young this season. Get a new coordinator and go through the necessary growing pains, and be tougher next year. But even if we fire Mess, the offense won't be better this year.