I never considered an indoor CQC before. If i wanted to do that I would have to heavily modify my CA, or my GBB. What are your thoughts on putting a velocity reducer flash hider on my GBB? I know its not conventional, but the challenge is half the fun .
i would recommend putting a little bit of money into a dedicated CQC set up.. find a platform you are comfortable with, and roll with it! there are endless CQC oriented variants of the popular M4 platform, there are also endless SMG and pistol's to choose from.. both gas, and electric
personally, i prefer the P90 for CQC. you get the short design, with the benefits of an AEG.. the only downfall that jumps to mind is the magazines, but airsoft costs money just like anything else in life!
also, you can rent all the gear needed to play at the VIP arena, that is another thing to keep in mind.. you can come out and try the place out without dumping money into a new setup that you might not even want to use if you decided CQC type games aren't your style.
if you want to discuss weapon platforms some more, shoot me a PM. i'll also answer any other questions about vanguard's venue, or anything else you are interested in