I would NOT want to crash land or belly in on that tank; rather than crash & burn, it would be crash and BLOW!
Would much rather have a jettisonable tank like the fighters used in WW-II (and beyond) - if you got in trouble you could dump it over an uninhabited area and let it vent off on the way down or auto deploy a chute. Other than that i’ts a great idea.
NG is no more dangerous than AVGAS. I do however see an issue with weight. The tank will be quite heavy.