Maybe you could have an AUX button you click at the bottom of the mixer to show the AUX Tracks ?
And how many AUX tracks do you need ?
In the pic I have 5 RT, 2 Mid and 2 Audio.
These will be just like extra Audio tracks that you can move RealTracks to so they will be playing from a file like a Performance Track as you can only have 7 playing from RAM.
You could have 16 midi tracks.
Would that work for what you need ?