At the end of the day, please remember that (most of) Volumio is a GPL licenced piece of software. People are welcome to improve/tweak things as they please. If those changes are helpful for the community, they will probably get merged into the main tree as Volumio see fit.
Also please remember that most of us here are just like you – we enjoy tinkering with these things, but this is something that we do during our free time 
Either way, I had some time in my lunch break and was curious so looked into this and figured out a really quick way to get things running - not all features work, but this should (mostly) work on a pi4, but don’t expect help when things break 
Good luck
I would love to see some benchmarks of this on a SSD/USB device vs an SD Card when it comes to (booted) Volumio performance…