I assume you're well-connected in Saudi Arabia, but leaving is expensive. This is exactly what you want for cooperative caching. If you think it's free to do cooperative caching, then fine, but if it's not free, it's not a good idea. ISPs care about bandwidth savings. In the paper, we do have graphs that show corresponding savings for bandwidth utilization.
Images are more cachable, and images are larger on average.
I don't remember the details, but I don't believe we saw a correlation between size and cachability.