Melmoth and Zoso from Killed in a Smiling Accident tried their hands, or rather voices, on their first podcast. It's a review of what happened in 2008, both in the world of MMORPGs and on their blogs. And one of the subject they talk about is that there aren't any good mech MMORPGs.
Well, the last good computer version of Battlemech I played was on an Amiga, I could never warm up to the real-time shooter versions on the PC. But Melmoth and Zoso have a point that mechs would make a good subject for massively multiplayer online role-playing games. Not just because of the setting, players walking around in giant robots. But also because of the heat combat mechanism. The big difference between mech games and other games is the concept that if you fire a weapon or do other special actions, that action is producing heat. Heat slowly dissipates via heat exchangers. But if you start firing without pause, sooner or later your mech will overheat and shut down.
But that isn't all. In most mech games you can design and build your own mechs, which is a much more interesting form of character advancement than gathering gear for your wizard in some fantasy game. In fantasy games there are no limits, you can always grow stronger. In building a mech you have a limited amount of weight and space. And you need to balance the equipment, if you put in too many weapons and not enough heat exchangers, you'll overheat after the first salvo. Different weapons are optimal for different situations, there is no one best build. All that would make for a rather interesting MMORPG.
Imagine a mech MMORPG in which players start with a standard, small 20-ton robot. Instead of leveling up, they gain pilot licenses for bigger and bigger mechs, up to the maximum of 100 tons. But from that point on, character development is horizontal, not vertical. During your adventures you gather various pieces, which you can use to build different mechs. Having every possible piece of gear in the game doesn't make you stronger than the other players, but gives you more options in building your dream mech.
It doesn't have to be wizards and elves all the time, you know.