Hope for the 7D version too please!
7D is unfortunately the hardest model, as it has trouble with many other features that fine-tune image parameters (even the good old FPS override and HDR video). I think it's easier to port it to a model from the same generation (550D is probably the best match), then figure out the dual digic issues.
The first step in porting this is to grab adtg_gui (see first post) and compare the 1080p and 5x video modes. There will be a lot of registers that change their values, but you only need a small subset to configure the crop mode. You need to find it by trial and error; it's very time consuming, but there's nothing to compile, just time to sit down, play with the registers, and write down your findings.
BTW, a while ago I've tried to reproduce Greg's full width LiveView
on 5D3 with partial success. There is a 3K video mode preset in adtg_gui, with broken preview. You can, however, use the grayscale preview from the raw recording module. I'm publishing it in this state, maybe some of you can figure out the missing bits.
i got black dots in 1:1 and 3x3 mode.
This was a side effect of the vertical stripe fix. I'll undo that change, because it didn't really fix the vertical stripes (it only made them a little less noticeable, but you still have to fix them in postprocessing).
2nd thing i "noticed" is that 1:1 mode is extremely overexposed compared to 3x3
Probably the other side effect discussed in the vertical stripe thread (linked above). Will double-check, just in case.
I'll prepare new build with the vertical stripe fix removed (back to the good old method).