I'm not talking about glass sheet sizes, I know you can get...

I'm not talking about glass sheet sizes, I know you can get large glass sheets. My company fits large glass to shopfronts all the time and to that end they are mostly frameless glass with fins, to fit the current look that designers and architects are after these days.
So you have brought up the size of 3.6m x 2.4m in your post, I dont care if its float, laminated, toughened, starfire or your low E example, lets get a CPV window done that size. With one external frame.
So going on your calculations when the window is done with one external frame it will be 8.64m2 at 30 watts max output per m2 it will put out 259.2 watts max. Now there is a decent output for you.
I look forward to seeing this made so people can see it can be done. I will say right now I don't believe this can be manufactured as a working CPV window.
Just a comment on the Low E Glass. You may not want to use that as it won't let the light that the CPV film needs to operate and produce power. Low E Glass is already covered with metallic films to stop IR and UV.