re: Basis for changing QB's...What makes sense?

I am not trying to answer "WHAT MAKES SENSE".
I am going to give you my perception of what I expect:

If JJ is really ever reinstated, then I would bet you anything he sees the field in short yardage situations, both inside the 5 and on 4th and 1.

Other than that JL is going to start until he messes up.

And if its late in the season before JJ is reinstated, JJ may also be #3, behind Mett - if/when JJ returns. That is, if Mett gets to replace JL due to some minor injury or just gets reps due to LSU being up by a zillion in some games, and if Mett does well, then, because Mett is a pure passer and JJ is not, Mett will move up to #2 and maybe even move up to #1.

And regardless of whether JL or Mett is #1 when/if JJ is reinstated, JJ is not starting unless the #1 does not get the job done on the field (due to chemistry and also the pure fact that JJ would not have been in the mess he is in if he had not made at least one mistake that night, being out of bed at 2 AM.
I could see JJ getting playing time in short yardage vs Bama.

Now.... we shall see.