Extending menu/pages musicbox_webclient to show dabradio; equalizer; and softvol sliders

Creating my own Sonos, and got my headless setup running step by step.
Figuring out ALSA, DAB radio antenna, spotifyd, bluealsa, systemctl, playerctl, and a lot more. Still have to attach my hifiberry, and configure usb audio CM106.

My audio sources (mopidy, spotifyd, dabradio, audio in) all have a dedicated ALSA input, having a dedicated softvol, subsequently they are mixed into the equalizer before output to the 3.5mm jack.

Now I have my setup running, now I want to have a clickable GUI.
My current idea is to extend musicbox_webclient: add a script adding elements to

When extending these list manually copying existing elements, and do some renaming, I can add a page which can be selected.
Next is to create pages for:
DAB radio,
and source selection (softvol-s of the inputs).

Anyone a better idea how to integrate all?
Can musicbox_webclient be extended, so others can hook in their pages? Currently additional pages are present for pimusicbox, which can also benefit from this hook-in.

And does someone knows how to configure next connection in ALSA?
arecord -D hw:1 -c 2 -r 48000 -f S16_LE | aplay -D hw:0