Please - some questions - have you researched any of these signers yet?  What do you know beyond what you assume?  Guess what - quite a few of these signers are SPPX - already all but heretical themselves (thus, the Luther comments).
BTW - priests may or may not be educated;  in the US, many catholics are more highly educated than their parish priests.  You state highly educated - track their careers - many of these signers are retired or where let go by former universities (you might want to see why?)
None of the signers currently sit on any recognized catholic university;  very few signers have published actual works, studies, etc.
*a few dozen* - well, facts are facts - out of tens of thousands of world theologians, you have less than 65 signers - yep , a few dozen.
Let's have this letter peer reviewed by colleagues recognized in their moral/sacramental fields - how do you think that will end up?