Did you end up trying to see if the Condor T&T pouch would fit with the annex clips?
Yes, see this link. My current usage is the final update at the end of the thread.
The wall will sag of course with anything of moderate weight hanging from it. But if it's any consolation, it will only really sag if the bag is open. Also of course if you have something sitting under the pouch (like a horizontal accordion file), then you won't have any wall sag. Last, if you're willing to attach the Brain Cell to the other side of the wall... (I didn't like that).
I don't know if this has been mentioned elsewhere, but the Smart Alec's Lower Modular Pocket fits perfectly within the Brain Bag. You just clip the upper and middle gateway clips until the loops where you would have put the annex clips.
It hangs off of the bottom by a little bit.