Digital camera needs multiple motor and a relative large battery. just look at the size of NEX7 or the Fuji Por 1. They are already bigger than the CLE and they are only APS-C sensor. You have also suggested to use the components from 5D. This will not be a small camera.
Leica lenses are"smaller" due to there is NO AF and NO electronically controlled apertute. Look at the 4/3 lenses, they are even bigger than the Leica lenses.
Nikon holds the patent right on their on sensor AF sensor. Do you think that they will allow any body to use it??
If the FF mirrorless can be built so easily and cheaply,whay nobody is doing it???
I am not saying a good mirrorless cannot be done. It just have to be compromised and canot satisfy every body.
What "motors?" ... no film to be transported in digicams. I want them to do away with the mechanical shutter too ... Nikon had an electronic shutter already way back in the D70. No noise, vno vibration, no bulky shutter mechanism unit and best of all: native X-Sync all the way up to 1/8000s! :-)
NEX-7 body size would also be perfectly fine with me. ;-)
And if the body/chassis is made from solid magnesium alloy or even more advanced "liquidmetal" (TitanAl-alloy), proper heat dissipation away from FF sensor is no problem either.
Powerful DIGIC + electronic components are no issue either and a LP-E6 battery [as in 5D2,3 and 7D] is not overly large ... it would hold enough juice to power fast hybrid AF, metering, hybrid viewfinder and back LCD and still be small enough to fit into a compact mirorless camera body. It would also allow many Canonites to use only one type of battery and charger, which would be very welcome. :-)
As far as lens size is concerned: electronic aperture without manual aperture ring takes less space and allows for more compact lenses. Ring-USM AF units are also extremely compact - unless we talk about big-ass super-teles with really large and heavy lens elements. If it was up to me I would make the zoom-lenses for the new mirrorless without focus ring and without manual focus. 99% of users will not miss ist, if the AF is up to speed. :-)
Those who prefer to manually focus may use their existing M-mount lenses.
Hybrid-AF ... with in-sensor-plane phase-detect AF - Nikon for sure holds some patents there, but I doubt they got it totally locked up. Canon hopefully also has patented some of their "ideas" in that direction.
After all, even LPA's monopolistic patent-reinforced hold on remote radio-flash-triggers did not last forever ... and had gave way to competitive solutions as in Canon's new 600EX-RT flashes. :-)