I have a thought for a feature that doesn't seem to be there yet.
With our EF lenses, the camera knows (and can quickly set) the focus distance. The computer in the camera can easily calculate the DOF from the exposure. They already offer built in exposure bracketing.
Why not offer focus bracketing? With a USM lens, the time required to shoot (say) three successive photos with three different focus distances would be minimal. Perhaps setable for how many and what the end points are. I've seen it done manually (it is certainly easy to do that way; I sometimes do it just to be certain of capturing a landscape just the way I want it).
Seems like something that would, from time to time, be very valuable to have. And the ability to combine the photos just as one does with HDR would make for potentially fascinating photos.
And if this is buried in menu 174 of my 5D3, my apologies for not having read the manual enough times to find it...