Thanks for the answer.
I think you are right - I thought too simple.
Will try to adapt the existing emulators a little better. Unfortunately the emulators don't seem to be set up well for the device. MAME, FBA, FCEUX (NES) and one of the two GBA emulators are good. With the PSX emulator and PICO-Drive, the aspect ratio needs to be adjusted. I am severely disappointed with the GB emulator (Gamebatte) - not a pretty picture.
Worst out of the box experience I've had with a PocketGo device.
The device definitely needs software-tuning. It's a shame to sell such a well designed device with this poorly tuned firmware. Pocket-Go is once again relying entirely on the community to fix this.