Building a non-permanent mix/control room in basement? | John Sayers’ Recording Studio Design Forum archive

Hi! First post here, this site is excellent! Anyways, here is my situation. I recently moved into a new house, which has a large room off the house (used to be a two car garage and is 22'x24'). I use this as a live room, band rehearsal, etc. However, I want to build a separate control/mix room in my basement, which is right next to this room. We are renting this house out in the country (no neighbors to worry about) so I don't want to build permanent walls or anything in the basement. What I am looking to do is build an octagon shaped room with movable walls to mix in. The basement is unfinished, all concrete floors and wide open so the reflection is ridiculous. I was thinking a room around 11'x11' or so from one far end to the other...but want suggestions. Basically, I can put this little room anywhere in the basement, because I want the walls to be movable. They will be about 8' high reaching to just below the basement ceiling, and I was thinking of building the walls with simply 2x4's and owens 703, with some fabric over the inside of them, kinda like huge gogo's to mix in. This room is primarily to mix in, so would building the walls with 2x4's, absorption, and fabric work or would this create too much absorption? I'm not really looking to build an actual wall with dry wall and everything, because then I would just have to build more absorber panels to hang on them...so why not just build complete absorbing walls??? Would I be better having some reflective surfaces in this mix room, or is this idea just ridiculous in the first place? I just need a nice control room area in the basement because I hate being in the live room while tracking bands. I'm looking for the best solution without having to build a permanent room in this rental. Thanks!