I think this is a very good idea. The loudness track could have various layers that can be quick-selected. In addition to the LUFS there might be a layer with the peaks, where we could set a threshold value above which the line is being drawn in red.
Another approach would be a custom integral time setting for the loudness curve; the default should be if set to EBU128, but if we could also set it to 0 samples, this would actually be peak, not?