If the future becomes more "mirrorless", just keep the form-factor of a DSLR. I don't want a point & shoot looking camera with interchangeable lenses...
1) Why did you respond to this thread again after 3 weeks out of nowhere?
2) I already mentioned several times the possibility of simply having a big empty case full of air, if you wanted to have the size of a DSLR anyway.
3) Most people want as small of a camera as possible, as long as it fits your hands. Meaning a full size DSLR case full of air would probably be a niche product. A collapsible hand grip that folds out to a comfortable size but then folds back down into almost nothing to fit in your pocket is the most sensible solution, rather than a big bullky box that can't be made small no matter what.
Still, I imagine there would be at the very least a 3rd part market for big bulky cases for those people who wanted them like you. I wouldn't worry too much. Sort of like you can go buy an underwater housing for almost any camera these days, I imagine at least some very popular camera models would have "large grip" housings you could buy to slip them into, etc.