Knuckles_waterandroidMGE is now restricted to the default classes (Scout, Soldier, Demoman and Sniper)
So close.
Sniper is a default class. Here's the default config for MGEMod.
We've updated our config file to those class settings, which limits classes to Scout, Sniper, Soldier, and Demoman on most arenas, and limits them to just Soldier/Demo on certain arenas like Endif.