I don't see any problem with having to talk to invisible firmware.
Surely that's normal for devices with firmware?
In this case, it seems even better for Plan 9, because the OpenGL/ES engine is in the firmware,
so we don't need to write or port one, just talk to an existing one.
It's similar situation to a wireless device I drove some time ago: apart from a slightly strange protocol to
talk to it, the firmware did all the work (as on the Orinoco cards),
the interface was quite high level, and there was no need for MadWifi etc.
I didn't feel hard done by because I couldn't change the firmware.