I wouldn’t call it impossible. I’m sure it is possible, but perhaps not practical since it would need resources to run.Yea exactly. It would be useful, but maybe impossible!
That said, this could be more easily implemented in a computer editor, where you have expandable CPU and memory that’s not eating resources that could be more useful in other areas (like modeling amps, fx, etc). You can do this right now in a DAW, but it would be cool to have a LUFS meter integrated in the computer Editor. However, that would require for the device to double as an audio interface, which the Kemper doesn’t do. This means this is more possible with the Axe FX or the Helix.
If you’re asking for something more automatic, then that would be a bit harder since it’ll not only depend on the inherent loudness of the profiles, but also how hard you pick and maybe other factors. Unless, the device could somehow store metadata of how you play those profiles and then allows you to balance all of them with one button press. Then again, this would require valuable resources to pull off.