Imagine you could get rid of the glass back and replace it with the material of your choice

It seems as if the general buildup of the Device is like it was with the iPhone 4(s)
there are 2 screws on the lower end which lock the backplate in place and when removed release it for easy access and maybe replacement of the back?
so replacing it with something more sturdy seems legit? even though production might be a bit complex it definitely seems possible as it did happen for the iPhone 4

A cool idea is the solar back panel, but it would surely interfere with Qi and NFC? so not a realistic possibility, but a PC/Plexi/Kevlar back might very well e on its way from 3rd party suppliers.

If google sells enough of these little beasts demand for replacements will be striking? even if it is sturdy? which it does not seem to be as we have already seen some cracked backs :P

also some black rough anodized aluminium might be a good idea (not the glossy/flat stuff Apple uses but traditional as it was on the HTC Legend and is on the OneX DesireS??)
 
Velcro (hooks)

..but seriously, a stronger but identical looking piece of glass/plastic that is less fragile would be just fine.
 
Carbon Fiber is the best solution. That or a nice billet aluminum. Carbon fiber is extremely strong, extremely light weight(depending on weave/construction), it is a bit more expensive than plastic, but it isn't ridiculous. Plus it looks VERY nice and many options in looks with CF.

CF would make this product PERFECT looking I think.
 
same stuff Carbon Ceramic brakes are made of :)
or Napa Leather
or fake synthetic leather
 
Like Kevin Spacey said in that incredibly weird voice, Krytpnoite! That way Superman can't get his grubby little paws on it.