neat idea, but...
Lipo don't burn so much as they explode. there's a youtube video out there somewhere of a 6000 MA, 11 volt Lipo in an ammo can. they were trying to build a safe place to charge indoors, and were testing it. the can had a 3 inch circular hole cut in it, with mettal dryer ducting to remopve the vented gasses incase the lipo burst.
the pressure wave of the explosion was enough to tear apart the ammo can, even with the huge hole in the sside to release the pressure. There are other videos out there 4000mah batteries being set in the hollow of cinderblocks, and breaking the block when they burst.
They do make a Nomex bag for charging small lipos in, usualy under 1500mAh. it won't help if they explode, but the smallerone usualy vent and burn, the bag can't totaly stop that, but it can limit the size and severity of the fire.
But all that said, Lipo is safe. It gets a bad reputation because its not as harmless as your average AA battery, and people fear what they don't understand, but the percentage of Lipo that do explode is far lower than the percentage of Bic lighters that burst in people's pockets, or the percentage of houses that burn because a gas can in the garage burst on a hot day, or cars that blow up in a wreck.
Most kids toys now use Lipo. An example is Airhogs. every one of there planes, helecoptors, flying boats, whatever, has a Lipo. Lipo in the hands of kids. and yet they are safe.
