Well we all laughed at FV's strategy game colloboration Velox et Astrum, but take a look at this. You may have heard of the RPG series known as ``Broken Sword''. And a small team of ~15 people managed to make a sequel to Broken Sword 2.
Rather than asking, I'll just dump a potential storyline / character thingy here.
You, the protagonist, are either unconscious or dead. The homeworld of the game is within your mind; an endless void of whitespace, with a small wooden shack floating on a small chunk of earth. Once you float inside the shack, you'll find a cloaked stranger (An older/alternate/etc. version of yourself). He introduces you to this existence, and explains the existence of magic, and other beings like yourselves that "exist" around you. This whitespace area acts as a mana repository; perhaps it can change color or something the more mana you collect in-game. You are given the option to move between this white-space world, and a "community pool of minds" of sorts, where you can see other players (by default, cloaked strangers, until you meet them), and jump into maps with enemies, or temples to learn spells and gather mana.
Tangible objects, like swords, don't exist in this world, so magic is one's only weapon. Each player can spend mana either to increase the power of their spells, to create new spells, or to add to their shield. Default spells can be learned at temples, while more advanced combinations must be experimented with in the homeworld. If a player falls in battle, they are merely sent back to their whitespace, sans shield.
That right there is my dream game, sans a lot of stuff that I don't see any reason to type yet. They might be overused, but alternate selves, death, and being highly unaware of obvious things are some damned good plot additions. I envisioned this game as a 2-d side scroller, something akin to MapleStory (at least, control-wise), but I doubt that a lot of what I wrote here could easily be coded.