This has been suggested (and rejected) before.
Your proposal makes most sense on big screens, which isn't necessarily the norm.
There are already (at least) 4 ways to switch between inputs:
- WiiM Home App: Browse tab, Source Input
- WiiM Home App: Device settings, Audio Input
- WiiM Home App: Store any input as a Preset. Can also be enabled via the WiiM Voice Remote.
- WiiM Voice Remote Source button. Admittedly, cycling through the inputs isn't the most convenient option.
I might have missed other ways to do it.