It seems I've participated in discussions about a hypothetical multi-band dynamics processor before, either here or on Wayne's forum, or both. If you plan to divide the dry audio path into multiple bands, process, and recombine them again, this is not trivial and the optimal crossover topologies for loudspeakers are not the same as ideal for this.. I would used "derived" crossovers that have a less steep slope (in one passband), but allow you to put humpty back together again neatly (ignoring the gain processing)... (1-x)+x=1. Changing the gain of the bandpasses will hinder perfect reconstruction (1-x)+Nx does not equal 1, but whatever.
===
Back last century I though about designing entry level sound system mixers (for beginners) that used dsp and were smart enough to recognize the different musical instruments or vocals and EQ the individual channels to deliver a target sonic template and final mix. My conundrum was that the technology to do this was too expensive to sell to entry level customers, and the professionals who could afford it would never tolerate a robot mix person inside the (top)box.

JR
PS: I would be one of those curmudgeons unenthusiastic about an after the fact "fix the final mix box", but I am not your target demographic.
