I always thought a mmorpg that is based on the samuri, that has a control and damage system kinda like bushido blade.... so it isnt all just click here, attack there... each fight is literally about life and death, that you need to have timing and skill... and instead of just having high level bad guys with more life, they are quicker with more skills etc taking the grind out of the mmorpg...also you would have life and death areas, so to start with, if you die, you wake up again in some hosiptal, cured and ready to go. but later on in the game, you have areas that you can die, you character being totally wiped from the game if they die. They can also sustain injuries, so if your leg gets sliced it may effect the way you fight (maybe not as quick, or change effectivness of stances)
also make for some wicked PvP, you can have the area where you only attack with sticks so you dotn kill each other, but you could also have the life and death pvp where you character can die etc.
Also I think a mmorpg, or just an rpg based off the dark tower series by stephen king would be cool.
Or a true survivalist mmorpg... based on any apoc, zombies, nuke, plauge... all good.... just one where you need to think about food sources, housing, water etc (which im sure people have already sugested)
most of my idea involve un-grinding the mmorpg....