I use both the 1-138s and A-138n as sub mixers, esp. the "n" version as it's DC coupled. these are some f the very first modules I own an they still are of a great help, esp. the "n" version, which can handle adio and cv signal (not the "s", which deal with audio signals).
I'd love to see an iteration of the MIXBX with cv over the tracks level/pan/send for sure !

by the way I have also gave the Squeeze of Feedback a test in parallel compression taskes (on beats), and I am very pleased with it, I'd probably get second one for stereo stuff.