I think that this just can’t come along soon enough.
“MiMiX is a mixer app for Audiobus. With MiMiX You can take total control of mixing of Your favourite Audiobus enabled apps’ outputs in the most convenient way. Just insert MiMiX into the Output Slot of Audiobus, even into multiple chains to mix the sound of the connected input or effect apps. You can even insert MiMIX into the input slot to send the mix to an other app, like a DAV to record the mix.”