I Nicogw,
I'm not an anamorphic shooter, but I tried the 5DmkII RAW mode. The 1880x720 res I tried is slightly thinner than 2.35, but of course is just an anamorphic crop, not a true anamorphic.
The thing is that I see a huge difference between the mkII and mkIII: the mkII RAW image is still full of moire and aliasing and if you can't shoot 1:1 crop is practically unusable, and the digic-4 processor can't hold a bigger res.
But again, this is my opinion and judge after I tried it fort 4-5 days. Hoping ML team makes some miracles again ;)