The 5GB is just the text.Images would be another terabyte or so, and you can't compress them any further.
That'll probably happen when there are terabyte flash cards.
Forgive the self-promotion, but CleVR sounds like the sort of thing that would help. It has a free photo stitcher and easy hosting of the virtual tour. It supports hotspots, so you can click to move between locations.
The opposite of a correct statement is a false statement. But the opposite of a profound truth may well be another profound truth. -- Niels Bohr