Your idea is very good, but is not quite the same, I think.
I'd like to act (beyond the "saturation of global volume check") on extreme final volume of each channel, also, in the "General" section, by adding a "Final Mix Volume" bar under the "Initial Volume" bar (because this one, as its name tells, is only "initial", and can be changed in the song, whereas I'd like one that wouldn't (only used when song is finished, so, as a real mixing tool))...