There are a lot of different meters, but to have a constant scale of some kind beside the meters is mandatory. You have implemented videometering (waveform) on preview-sources, but no real output audio-meter. In the Nordics we use Nordic scale, with 3 colours; green, yellow and red. There are different variations of this (Nordic scale is an analog metering, where 0dBU is -18 dBFS. First thing to do is to put the dBSF-scale there, and maybe in the future add different styles. To define 3 colurs in dBFS would also be nice; green up to -18; yellow from -18 to -12 and red from -12 to 0.
Magne