Marsu, have you looked at the costs involved to go 5DMIII all the way? Its cost $3000+
The trinity of FF zooms, 16-35,24-70,70-200mm they set you back $5000+
Now if you bought a FF, and want bokeh, you will want to go L-Series, 24,35,50,85 & 135mm? Cash outlay $5000+
That's a pretty steeeeep up front cost, to get all that one would want on a FF for video.
Lets see a 70D, cash outlay $1200.
The best APS-C zooms Tokina 11-16mm f2.8, sigma 18-35 f/1.8, sigma 50-150mm f/2.8, cash outlay $2300.
The primes, well you are only going to go USM equivalent on a APS-C, so you already have 18-35mm f/1.8, so only two more needed sigma 50mm 1.4, canon 85mm 1.8. cash outlay $1000.
So lets see for the cost of just the FF zooms, you have all you need on an APS-C to shoot high quality film including decent bokeh.
So in short, folks are buying the 70D for the continuous AF to shoot semi-professional quality films on semi-professional budgets.
If you want wild life / action the 7D is your axe because its 8fps. There is not much for still photobugs to want to upgrade to in a 70D, its got the same sensor size as rebels & the other aps-c, and it has a worst view-finder focus. Its not a prime axe for still shooters. You can put out a poll to get convinced, folks are upgrading to 70Ds from rebels, 60Ds, and 7Ds for the continuous AF video.
So again I ask, is it possible to have a 70D build that targets RAW video & HDR video as first functionality