Vocal/Amp Booth ?

I've been doing a bit of thinking. I have a studio/rehersal room with my band, and we've been doing a bit of recording there. We are planing on building a control room, and think pretty hard about the CR interior. Since I'm not sure sound-isolating the control room perfectly, to be able to have open mics and live monitors will be in the budget (since we're going to work as hard as we can on the CR acoustics. I was even thinking about making the CR walls, and don't even close the outer side of them (just put something in the inside of the wall, and then put some diffusers and such inside them) To be able to have open mics and live monitors, without risk of leakage, i was thinking about building a well isolated vocal/amp booth in one of the corners (I would build all 4 walls, and a cealing. The floor could be the same) The vocal booth needs to be able to fit only one singer at a time, a 4x12" guitar cabinet or a 8x10" bass cabinet, so any extra space isn't really wanted (since we don't have to much space in our rehersal room) I'm not planning on recording any stringed or wind instruments, i only (for now at least) only do "standard" (drums, bass, guitar, vocal) rock bands. So everything could be inside the booth while being recorder except the drums. I would have the amp heads in the control room and a nice speaker cable to the speaker inside the booth the door doesn't need to be full sized, just enough to get a singer, and cabinets through the door) A rather small window (just to be able to see the singer while performing) would be prefered. But good sound isolation and very diffused small room is really what i'm looking for. So, how should I do it :) what interior size would you reccomend, how tall should the booth be, how thick walls and made of what, How large door and how should i isolate it, how large window and how should it turn (should it be behind the mic, on the side or on the back of the singer or what ?), how should i diffuse the inside of the walls and so on. I'd never use more than 2 mics and one pair of headphones in the booth at once, so i'd probably just put 2 xlr and 1 jack connector on the wall, so I'd wouldn't have to make a hole or something like that for cables. I'd prefer to keep the cost as low, without making it some useless junk