MMO Mech game, why isn't there one?

So I had this idea years ago when I started playing World of Warcraft, after hours of grinding levels at 2am, why is there no MMO mech game?

Let's be honest, mechs are cool, giant robots, everyone loves robots!
I'm not sure why it has not as yet been done, but if it does ever get done, I will be first to sign up.

Gear system: Well now, gear in MOST mmo's is pretty important as it is directed towards certain classes, and this would be no different.
Gear upgrades could be done as "salvage", this also adds the crafting (or in this case engineering) of parts for your mech.
 Salvage would be parts and items that drop off mobs and also items that could be broken down in to parts to make other items such as laser rifles, shields, power swords, armour etc.
you could have plans that can be researched over time or when you disassemble items, you have a chance to "reverse engineer" an item, either causing it to break and you lose the item, produce only parts or learn a new schematic.

Class mechanics: in most MMO games, you have separate classes to do specific roles, this would not be much different although I'm sure with some ingenuity, I could probably find a better way to do it.
In saying that, you could potentially have different professions locked to class and remove the tanking class altogether.

Well, that's what I think, do you wish there was a mech mmo as much as I?