M9K is the biggest weapon addon ever released on Garry's Mod. One of the reasons is due to its vast array of weapons.
With the way it's looking, custom classes aren't coming back. Only a select handful of players get to enjoy different weapons, while most are stuck using the same M4 or AK they've been using since day 1. For example, the assault rifles. Pretty much every single one can be added to the Heavy Gun Dealer's selection as their balance is already in line with the other weapons. New snipers and shotguns are where the problem is, as they are the dominant weapons of M9K. Some snipers, namely the SL8, Intervention, and PSG-1 are already in line with the existing SVD Dragunov and M24/AW50. It would make no sense not to bring back custom classes, but not open up the weapon selection either.