That isn't a Stryker thing.  That's a Mark Brewer thing.  The guy is a lawyer by trade (he initially made his name representing the Ku Klux Klan) and rarely misses the opportunity to sue the pants off a political opponent.  The fear of a lawsuit itself isn't enough to dissuade me.  That said, it's best to cross our I's and dot our T's, so to speak.

Michigan election law states that a Party's nominees cannot be nominated until after the August Primary but leaves completely open to the Party the means by which their nominees are selected.  

I tracked down a copy of the proposed two-fer rules and this is how the language deals with existing statute...

MRP would not technically be nominating the SoS and AG candidates at the early convention.  The early convention would only determine which candidates were eligible for nomination at the August convention where they would actually be nominated.  So, the only candidates eligible for nomination in August are those candidates who received the highest number of votes for SoS / AG respectively at the late-March convention.

In other words, the early convention would make someone the "candidate eligible for nomination."

I'm not a lawyer and won't pretend to know the ins and outs of how something like this would be perceived and handled by the courts should a challenge arise and should they even bother to hear it (though I have serious doubts that any court would disenfranchise voters across the state by eliminating a major Party candidate from the ballot when that candidate's nomination was done according to the letter of the law).