Bluez these days is pretty tightly coupled to modern desktop linux. IIRC the only official way to talk to bluez is through dbus (there are still a couple legacy ways through shared libraries though). I don't think Android seriously uses dbus though so that would be a pretty big issue.

And as a person running the latest mainline kernel on their daily driver laptop--I would not want bluez running the wireless peripherals on my phone. I can barely keep a wireless keyboard attached and working on this thing... in 2021.