5x reduction? Heck, you'd struggle to find common libraries that fit under those existing limits! jQuery is 88kb (Yes everyone can hate on jquery all you want, but it's still commonly used), which is already over the 50kb limit! At 10kb...

Modern camera's take pictures measured in megabytes, and you're suggesting the per image max be 200kb, and total images to be 400kb?! Two crappy quality images would blow that out of the water (Heck a single crappy image could).

I get that this is a prototype, and seems to be intended for mobile devices, etc. But those limits are already something you'd have to work for, I'd argue it's near impossible at 5x less resources.

tl;dr by todays standards a 5x reduction in those limits is just code golf.