Well, to fix the oversized MIX BX issue AND to add some final VCAs to the audio path, I would recommend having a look at Tesseract's TEXMIX system. With the Master module and a mono input module (4 ins, VCAs over level), you get your final VCA level controls. You even get to stick with the dual AUX send/return architecture for your effects. But the result fits in just 20 hp. Need more inputs? Just add another fader section!