OK you big dummy, let's do some math. Chewbacca is 2.28 meters tall which would translate into 7.48 inches. Assuming his feet touched the very bottom of the box and weren't in a plastic tray, the window come up 3/8th of an inch to short. Now factor in the thickness of the plastic tray and it's now more than half an inch too short. So, would Hasbro package the "premium" figures in a way that would cut off the head? While I personally wouldn't care, I think a lot of collector would be put off by that.
So, you could make the window larger, but then the Star Wars logo and circle with the figures head would have to be made smaller. That wouldn't look very professional next to the rest of the figures now would it?
Like I said earlier, look at how they handle these issues in the 12" line. I don't at all expect to see a case of tall figures, but I do expect some retailer exclusives down the road that include Chewbacca and Vader, just like they did with the big guys in the 12" line. Is that so had to understand since the precedence has already been set?
Now I could very well be wrong, so feel free to throw it back in my face next year, but right now based on what I've seen I'm sticking to this theory. Vader will be in some special packaging, possibly with half a meditation chamber and Chewie will be a store exclusive or worse some SDCC nonsense.