What I have in mind is something that shows the frequency landscape/range used up by each track/bus. So I could look at a set of scopes or sonogram type displays, or one single display with range labels indicating "this range of frequencies is dominated by track n" or some such thing, indicating which tracks the spectral content is coming from and where the mud and thin areas are in the mix. I know people say that doing a mix by ear is the pro way, but I like the idea of visual aids, and visual EQ is often advised to examine individual tracks, why not a whole mix?

I'm not 100% sure how to represent all this on one display. Obviously there are four "axis" to track (time, frequency, db, track/bus name), so it can't just be a flat sonogram, right? Maybe some kind of alpha transparency mask on a sonogram that highlights the total mix content of a selected track, while dimming the non-relevant frequencies.

I imagine this would need to be integrated into a host, since VST doesn't have access to track and bus names (??).

Anyone ever seen anything like this? Anyone interested in/capable of building it?

(anyone get what the hell I'm trying to describe? )

I think Blue Cat has plugins that do this, but maybe not built into an EQ.

stillwell has something like that i think and voxengos span has like 8 inputs but i dont think they have any eqs that do that just analysers

Schwa schOPE, IIRC.

Truth to be told, that doesn't really work. I tried this approach several.
Use see all the tracks, you see where the frequency clashes. Now what? EQ that frequency? From which sound? How much should you EQ?
Then you apply EQ, you find out that it doesn't really sounds that well. You spend a lot of time on it, trying to approach it visually without giving consideration to the sound. Then finally you find something that works. Cool.

Now the easy way. Close your eyes and sweep a notch filter on the offending sound, until you hear that this sound stops sticking out badly. If the sound disappears too much, then switch to bell EQ. Easy and much faster.

I was about to post something like this.
but basically its something like if you cant get the bass and kick to play nice find something in the bass that really masks the kick and cut that from the bass just a little then do the same for the kick if you really want to and things tend to fit a little better. I would say use your ears if your hearing to much mud and have really beefy guitars high pass the guitars while listening to the mix