We need a crossfeed/monitors/room headphones mix app as "effect"!
I searched, but didn't found any Audiobus effect app capable of creating crossfeed/monitors/room sim for mixing with headphones.
Even stacking EQs with crossed pans, delays to reproduce time gap between ears, reverb for the room...impossible.
Something like Isotope Isone, Redline Monitor or Crossfeed EQ/Head-fit (freeware) to avoid a big part of headphones drawbacks : unrealistic bass level, bad stereo imaging, too wet...
Put it at the end of the chain and you are ready to mix a lot better
You can use it with any Audiobus app.
Ppl with iPhone/iPad mix mostly with headphones...it is going to be a big step forward.
Make some noise !