Well, you see, my idea revolves around setting up a trackable field for every player, to detect their mouse clicks, and also the position, if they're casting. I'm using DGUI for the camera and a spellbar above the UI. It's gonna be a hero arena with Diablo style hero control and custom spell targeting (which is a lot more flexible than the built in spell system, and it even gives me control over cooldowns). Everything will be custom, I'll handle even the hero healths manually, so I don't even need Status, for example :'D
The trackfield itself costs quite a lot by itself (5624 trackables in total if 6 players are playing, with a trackable length of 104 units), and DGUI is quite costly too (although I won't use it all that much, only for the UI extension). But since I don't need missiles to be as complex as in Warlock, for example, a simple, but fast one is enough for me, so that I don't have to make my own, or hardcode every projectile.
So yea, that's my idea
But of course I've got much more ideas (local accounts stored on the player's PC, etc etc). What about yours? I don't think I've asked you about this.