Yes, I know, I am totally aware of 4 corner correction is not possible since HDMI and USB-C inputs are not connected to the Android board. But…
What if some kind of hardware adapter was developed by you, Screeneo/Philips, capable of distort an HDMI input based in the current Picopix Max 4-CC settings?
It could be something like:
1 HDMI input
1 HDMI output
1 USB input (both for power and control)
Internally, the adapter mainly would be composed of one specific chip capable of horizontal and vertical video keystone and one microcontroller capable of controlling that chip (via i2c, SPI, uart…) and also talk with the PPM (via USB)
This way, you could develop some kind of proprietary USB driver and/or Android service in the PPM that could detect when the adapter is plugged in and automagically mirror the current Android 4-CC settings into the adapter. Final result will be coherent and transparent for users! (apart from the extra adapter plugged in, of course)
Chances are slim that you put the required effort in something like this now, but I’d happily pay 50€ for it if you make it! Think about it as one accessory more like hard case, remote or tripod.
Actually, the perfect adapter would have both HDMI and USB-C inputs, and one single USB-C output (for video, power and control at the same time) so USB-A port remains free.
It could also handle ARC while you’re at it.