Perhaps Matt and company will be updating the QA401, not just for the sake of progress but because of the AKM disaster. ESS, as one example, claims to be offering better ADC parts at a competitive price. How well they actually work is TBD. If they meet the marketing release, a new QA40x would come that much closer to an Audio Precision system for far less money. (Not to 1 MHz, though…) That would all involve real work on the part of QA, obviously.
Maybe QA would consider retaining the BNC inputs and outputs for the unbalanced connections, but go to XLR for balanced/differential I/O in any new product. Perhaps another step or two of attenuation, too. With these two advances, your other desires could be easily managed with passive external boxes as you need them. Of course, that doesn’t help an existing QA401 owner…