A small EOS FF camera would still have large lenses though.
To me, weight is more important than size. A Canon 1DsIII weighs 42.5 oz./1,205g, a Sony NEX 7 weighs Approx. 10.3 oz (291g). That's a difference of 30.2 ounces! A FF mirrorless would only gain an ounce or so, say about 12 ounces total.
Granted but, I'm assuming you would still want to use EOS lenses on this mirrorless FF? You'd save weight on the body but, for example, a fast 85mm is still going to be a heavy thing, no matter what system it is designed for.
I don't like the big, heavy and slooow focusing 85 L. I use the 85mm f1.8. My advertising clients aren't impressed with "paper-thin-DOF" And I would only be interested in a mirrorless line that had it's own lenses.
Do you shoot a 1DsIII right now? it would seem silly to compare it to an NEX 7, a camera that is quite different. Are your interests moving in such a way that you actually would replace a 1DsIII with a FF NEX camera?
I use a 1DsII with an 85mm TS-E for table-top work. It is mounted on a FOBA camera stand and tethered to Capture One.I Never hand hold it, too big and heavy.
For hand held work I use a 40D usually with a 85mm f1.8, using CF cards instead of tethered.
An E-mount Zeiss 24mm f1.8 weighs 7.9 oz (225g) plus a NEX 7 at 10.3 oz (291g) (excl battery & media) plus 2.1oz (57g) for the battery = 20.3 ounces. For comparison a Canon EF 24mm f/1.4L II USM weighs 22.9 ounces. So yes, I'll switch to Sony's NEX system for most of my work.
BTW I'll test the NEX 7 with a Tilt and Shift lens, all the NEX cameras have peaking focus
, which should work well for table-top. Here's a video to show peaking focus
That's one of the good things about Sony being in the pro video business, maybe we'll get Zebra Stripe next.