You have other fire hazards like the rubber fuel lines on the drivers side, transmission fluid through rubber hoses, oil through oil cooler lines, etc.. all which can ignite.
Alcohol can ignite if exposed to an open fire. Heat wont ignite alcohol unless pretty intense, and typically alcohol will evaporate before igniting. It is not as flammable as gasoline.
You have options, typically the issue is cost. I have done a few Buicks high 8 sec/low 9 sec and used fuel cells in those applications. Just recently setup Dennis Hogans car with a 1 gallon cell in place of where the battery is located. Gene made the brackets attaching it to the core support. just adds $$ and complexity.
Neat thing is you have from GM a "firewall" to protect the occupants. This is why these systems are typically done under the ood where this type of protection is afforded. At least the system is not pressurized while driving around, so gravity would be the only issue in case of an impact. And if the impact where so severe to rupture the tank, you have far greater issues to worry about.
Even a stainless steel tank with steel lines can be ruptured. And as always, you can mix water with your alcohol making the system completely non-flammable. The down side is a degredation in performance in exchange for an extra degree of safety.
HTH