Sorry, the MJPEG frame rate patch doesn't actually change the rate at which the image sensor is scanned, which is locked to 30fps on all Panasonic G-series cameras in MJPEG mode. Patching in a different MJPEG frame rate only forces the camera to duplicate or drop frames from the 30p video stream, producing a choppy simulation of a different frame rate.
Is it a limitation of the scan out of the image sensor or of the data processing downstream? And then is that a limitation in hardware programmable by firmware or is it fixed in the wires and silicon? From your explanation it sounds like its in the wires or silicon and not accessible via firmware.