There are some issues after the new updates to the classes:
1. You cannot select weapon masteries from the books that came with the Gunslinger or Monster Hunter unless you play as those classes.
2. You have no way of getting weapon masteries from the Grim Hollow or Gunslinger Sources if you are playing as any of the Core Classes.
3. The Monster Hunter can only select weapon masteries from the Core Rules and the Grim Hollow Source categories while the Gunslinger can only select Weapon Masteries from the Core Rules and the Gunslinger Source categories. Neither of them can select weapon masteries from outside those two.
4. The Weapon Mastery Feat only allows you to select Weapon Masteries from the Core rules only. It Does not allow you to pick Weapon Masteries from other Source material like the feat should allow you to do by the very wording of the feat.
5. When Selecting Masteries for the Gunslinger or Monster Hunter you are forced to select which category to pull masteries from. In the event you are selecting multiple masteries they must all come from the same category instead of being more varied to provide a more customized character.
It is, very obvious that this was not the intention of how this was supposed to work. It adds a perquisition that was never meant to be there and creates a major limitation on something that should not have been limited in the first place.

I would not hold my breath on this one. Those masteries were probably meant to function more like class-specific optional features than true masteries. I think they want to draw a pretty hard boundary between core and third party material.