I'd find it really handy if there was a screen that would display meters for input and output levels, including peak indicators and also numeric values for current and peak levels too. In fact I'd be happy even if it was just the numeric values if meters are too much of a PITA to implement on the display! 
It would help diagnose faults elsewhere in the signal chain as well as making it easier to ensure that reamp levels are correct in a consistent manner. Plus it would be obvious to see if you need to adjust sensitivities when switching between different guitars.
For bonus points, it'd be even better if there was also a meter showing the current amount of gating for the gate stomps, much like the TC Electronic G-Major has for its noise gate. 
In case you've not seen one it's basically a meter that's empty but gets bigger the more gating happens. So as a note trails off it would gradually increase but if you did a couple of palm mutes you'd see it jump up twice quickly. It's useful for seeing if your gate thresholds are set correctly which is also handy if you switch between guitars with different pickup outputs.