OK, to summarize, and introduce some realism:
What would be lost:
Michigan Pistols (MAYBE), which already has no new new registrations after after the other law goes in to affect.
So the only people who MIGHT be affected by this are those select few who already carry Michigan Pistols, for this some would like to sacrifice the rights of every resident of Michigan so THEY may still exercise the privilege granted to them by there political masters. To keep THEIR they would throw the entire rest of the state under the bus, it's just like the Fudds who would be perfectly fine sacrificing everyone else's rights through an AWB, Magazine Ban, Registration, etc. just so they can keep their antiquated (1898 technology) bolt action dear slayer just a little while longer.
First they came for the socialists,
and I didn't speak out because I wasn't a socialist.
Then they came for the trade unionists,
and I didn't speak out because I wasn't a trade unionist.
Then they came for the Jews,
and I didn't speak out because I wasn't a Jew.
Then they came for me,
and there was no one left to speak for me.
-Martin Niemöller
Gun free School Zones exemption.
The purchase permit over riding the "gun free school zones" has never been tested in court, and is just a theory, and the fact that we have CPLs, and that "license to carry" seems to appear only in the title of the purchase permit, and nowhere else in law, and that the permit itself specifically states that it's not a concealed carry license, and that it expires after 10 days, I would think that it would probably not hold up in court, particularly after they interpret "legislative intent". Then there is the fact that very few states (none?) other than Michigan have any such "exemption", and have not had any issues, and the fact that no one has ever been charged with violating the gun free school zones law as a standalone offense when all they were doing was otherwise legally carrying a firearm within 1,000 feet of a school.
Since it would have to be argued in court anyway some other (possibly better) defenses would be the fact that the "gun free school zones act" is unconstitutional, and it has already been struck down once by the Supreme court (before being re passed unchanged again right after it), and that there was no Mens Rea if you did not know that it was a "gun free school zone". (To be a crime the prosecution must both prove
Mens Rea "The Guilty Mind", I.E. that you knew what you were doing was wrong, and
Actus Reus "the Act Itself". ACTUS NON FACIT REUM NISI MENS SIT REA "the act does not make a person guilty unless the mind is also guilty".)
What would be gained:
No more registration, or purchase permits.
Now lets look at the practicality of Michigan Pistols:
The average gun fight happens at a range of about 3 feet, lasts about 3 seconds, and 3 shots will be fired according to FBI statistics, they look nothing like what you see in the movies. It is extremely unlikely to the point of being astronomically unlikely that you will be able to fight your way back to your long gun that you left in your car, particularly if you are some distance away from your car at the time, and if you do make it back to your car, one wonders, and the prosecution will surely bring up why you do not simply flee the scene seeing as you had enough time to retrieve your long gun, and bring it to bear. Should you be attacked while in your car same thing, it's unlikely that you would be able to bring your long gun in to action in the confines of your car faster than your pistol that you already have on your hip, so the question then would be how did you have time to use the long gun? If attacked near your vehicle the question is still how did you have time to open your vehicle, retrieve your long gun, then bring it in to the fight, and why did you do that when you could have just used your pistol?
A long gun carried loaded in the car is useful/practical only in a VERY limited set of circumstances, such as:
You KNOW you are going in to a potential gun fight, and you will be taking the rifle/shotgun with you when you exit the vehicle, I.E. a patrol rifle.
You have been ambushed while en route to your destination, and your vehicle has been disabled/blocked in, and you are pinned down under enemy fire from some distance away. Short of being in a warzone, or an assassination attempt this scenario is unlikely.
You are away from home, and your vehicle is disabled leaving you stranded, and you must fight your way home through hostile territory. Short of SHTF, or the end of the world as we know it (TEOTWAWKI) with the complete break down of law, and order, and civil society (such as a riot, or Katrina style situation), or being caught behind enemy lines in a warzone this scenario is not likely.
You are paroling a large rural property, and spot a hostile (or predator) at long range, but in this scenario you would likely have time to access a cased rifle.
If you insist on taking a long gun with you in case of any of these highly unlikely scenarios, then that can be accomplished without the need for Michigan pistols. Simply carry a technical pistol, I.E. a stockless rifle, or shotgun (.410, or AOW) like the AR Pistols for example, or carry the rifle, or shotgun cased in the front seat (it does not need to actually be in the trunk, or inaccessible, merely unloaded, and cased (Or unloaded, and uncased, but taken down, such as an AR, or SU-16.). In any scenario where you would actually have the time to bring the long gun in to play in the first place you likely would also have time to uncase (or snap it together), and load it.
In short the untested gun free school zone exemption, and the convenience of the select few with Michigan Pistols in highly unlikely scenarios is not worth sacrificing the rights of 9,876,187 Michigan residents.