Although I do like the idea, I fear I have to be against it.
It has already been mentioned before, that certain classes with limited choices would be punished for no reason. You can only have one of what? Five crossbows? Eight bows? Seventyseven one handed weapons?
The second but most severe disadvantage would be that you are not indipendant in your choice of classes. You can't equip your build the way it suits you most, unless you have a lot of gold on your account. I don't like the idea to get punished for feeling the same about an item like the majority of other players.
Of course the most used items are the most viable items, followed by the best looking items. Now if I don't have a lot of money (and still want to keep my loom points, because I think they are an important part of further improving my character!), I will be FORCED to use inferior equipment and/or equipment that doesn't look well in my eyes, entirely killing any identification I have with my character.
Imagine how you would feel about not being able to use your weaboo stuff any more because there are too many weaboo fans around and you run out of money. And suddenly you have to run around with leather helmet, byrnie and nordic sword like everyone else. Great conditions for leading a Ninja clan or being part of it.
The suggestion goes against the idea of an RPG. It's more like "Day of Defeat", you connect to a server with class restrictions, and the only class left to be played is the rifleman, because the choices of the other players on the server force you to equip the M1 Garand / Mauser K98k. It feels unfair.
Some time ago I suggested something
similar, concerning the classes. I think it was around the time when there was the archer problem on the servers, and the devs nerfed dmg/buffed headshots. But still I could live better with such a system rather than one the determines your equipment. Because it doesn't prevent you of playing the class you want, you just don't get rewarded.