[corn-cheese]

I’ve thought about building something similar, but for an arbitrary number of sound sources, with a single flying fader, a small mono display for icons, and some buttons.

…hang on a minute, it already (kind of) exists: https://www.elgato.com/us/en/p/stream-deck-plus-black

[diggan]

Maybe I'm blind, but what you linked doesn't seem to have any faders, and instead have four knobs?

[nkko]

Everything already exists, which is no excuse for doing it again.

[NoxiousPluK]

Also check some of the forks of Deej; some already implement this in a DIY form