Isn't that just poor design in the first place? The X5 was severely crippled with that highly reduced datarate. They should have made it Prores capable right from the beginning (which incidentally is far less processor intensive and taxing than H264 encoding, and can easily be done to SD cards as per the BMD cameras). The tiering system for the X5 was always way out of whack. Plenty of people could have used Prores, but not many people really need Raw video (even if many 'think' they do). So to have low bitrate H264 on the lower priced camera, and then jump straight up to 4K raw encoding with all the expensive and heavy storage requirements that go along with that is too much.
Personally I would have been perfectly happy with an X4 that records Prores to SD card, and a slightly larger chip camera, and skip the interchangeable lenses. They've practically done this with the X4S without the Prores.
But going on from my last reply, is the X4S encoding on board the camera itself? If it is, then why can't we have such a camera for the I1 with its higher bitrate recording? If it isn't, and the encoding is taking place on board the aircraft, then why can't the X5S have H264 recording? And in that case what type of signal is the X4S piping through, and why can't that signal be recorded as Raw or Prores?