volume help from Newbie

Is there a way to get the SP808ex to change the levels of each track, when you're using all the 8 (4x2) individual outputs instead of the Master Output?

I know the manual says no, but I'm hoping maybe there's a workaround someone has discovered?

I would like to use this unit live without bringing along a separate mixer.

I've thought of just recording each of the 8 tracks at its proper level relative to the others, but then, I'll almost certainly need to tweek those levels live, and on the fly, depending on room acoustics, other musicians' levels, etc.

Any suggestions? Thanks!