S7G2 bootloader over USB

I'm trying to implement a bootloader over USB for a custom S7G2 device. I see references to the flash loader but we are running SSP 2.4 not 1.3 so I do not have those options.

I also see options to use the bulit-in bootloader but that requires the user to reset the device and for the MD pin to be toggled. The user has no access to the MD pin.

I would like to be able to plug in the USB and be able to upload new firmware. Is there any examples of this being done already?