That's an interesting idea. You'd probably need to extend them somehow or you'd hit your hands. I hope you were serious about this, and I would love to hear it/see it.
My guess is that what would happen is the sound would be very inconsistent for each drum hit, because the mic wouldn't always...
Exactly what I was going to say, however, don't build one unless you know what you're doing.
You're going to want a firewire port, a lot of RAM, a nice processor, and a huge hard drive.
If you've got a budget of around a thousand five hundred bucks for just the computer, you are in luck. I saw...
I pressed record and then started singing, but my computer didn't record it.
Also please move this topic back to computer recording and soundcards (whatever those are) because I'm trying to record on my computer.
I used this set up with a 58 (top unscrewed to make it a 57, though) on the kick, and 2 58 ripoffs as overheads, and the drummer I worked with loved the results. (Granted it was his first time being recorded :P)
I've never tried it, but the first thing I would do is put a bit of distance between the vocalist and the mic. Have the vocalist singing into the megaphone on one end of the room, with an omni on the other side? That'd probably pick up the megaphone reverb well.
You'll notice on all Rock Band and Guitar Hero games there is more reverb. They put reverb on it, as well as EQ it a bit lower to make it sound more 'live.' Some of the songs on Guitar Hero 4 really pissed me off, they were EQ'd funny and it screwed up the vocals.