In short, you cannot use the higher resolutions with uncompressed formats (RAW or MLV). The SD card CONTROLLER in the 6D is not fast enough to do it. You can use normal H264 compression, but it is lossy, so there will be some artefacts.
A faster SD card (above 40 MB/sec) will not help - the limitation is Canon hardware.
ML will let you try: the higher the resolution, the quicker the buffer runs out and recording stops with a "skipped frame" error (when I try it). You can record a few seconds of full-res raw video, but that is not long enough for serious work.
This is all documented here on the forum: use the search function.
There is also a discussion about writing new code for recording raw in lower bit depth (12-bit or 10-bit). You cannot do this now.
IF, and only if, this can be done by controlling other parts of the camera hardware, it MIGHT reduce the data rate going into the SD controller enough to permit higher resolution raw recording, but that would take a lot of work, and I would guess a new raw storage format just for cameras like the 6D.
I understand the issues, but don't have the skills to help the project. I wish I could help, but it sounds quite hard (turning off bits for the pixel data is fairly easy, but making effective use of that to get more frames to the SD card per second is hard).
I am very grateful to the team for what we do have, and for free.
S.
