There's a couple things to consider here:
1. Vontaze Burfict establishes a precedent
2. Much like Burfict, Myles Garrett has shown a history of dirty hits
With this in mind, the minimum suspension has to be based on the season long suspension of Burfict. Additionally, Burfict never used a "weapon" to attack his victims. So the formula for Garrett's suspension will have to be:
Burfict's suspension plus use of a weapon in the commission of the act. Burfict got 12 games.
I ask you, what is the value of the use of the helmet as a weapon? Whatever you may believe should then be added to 12 games and then you have the suspension due Myles Garrett.