USB-boot initialization trigger

[macmpi]

Capturing within a specific issue a setup problem that has popped up in several issues.

Currently USB-boot initialization is triggered by program_usb_boot_mode=1 detection in config.txt.
This had legacy reason as Pi3 needed to be initially programmed to support MSD boot, but this is no longer the case with Pi3B+ and Pi3A+ as they do support USB boot of-the-shelf.
That program_usb_boot_mode=1 step is not appropriate either for other devices like PiZero supporting MSD boot with specially-crafted SD.

So program_usb_boot_mode=1 detection in config.txt is no longer a good trigger for setting-up USB boot. Could you consider another, more universal, method to trigger such initialization?
(like a UI element in setup, or a specific flag "touched" file, etc...)

Thanks for consideration