Hi, I use magic lantern for a long time on a canon 600d and now on a 70d and 7d.
I always tried to shoot raw but the bitrate is always too high to have a fhd recording.
So I want to suggest you: why don't we try to shoot a jpeg2000 sequence?
The files will be more small and the quality will be much better than an h264.
A jpeg2000 could be 444 and 10bit.
Also dcp are made with jpeg2000 sequence stored into an mxf file.
I think that with this format every canon can shoot 4k sequence.
And I can't stop using horrible m4/3 sensor to be future proof :D
It would be nice. So nice in fact that you are not the first (or the third, or the tenth, or the.......you get the idea) person to have asked.
There's a sticky thread at the top of this section that gives a clue.