I have a 01V96i and have set its peak-hold on/off switch to one of the softkeys (called “user defined keys” by Yamaha). This really is a great feature, especially if you want to level two channels to exactly the same gain. So I’d like to support this feature request!
I have an additional suggestion to make: Together with the peak hold, the gain section of the processing view could display the actual db value for the channel (as done by many DAWs).