In looking at risk, I would be most concerned with what kind of malfunction could lead to what outcome. LiFePO batteries can be punctured without catching fire, and if a fire is caused by something else, they are not fundamentally very combustible. This chemistry is very different from Lithium-ion. In terms of add this to your house, there is low risk of them starting a fire, and low risk of them contributing to a fire in a significant way.

Gasoline in a car has a low risk of starting a fire, but a higher risk in the event of being exposed to a fire. Storing gasoline in a jerry can probably has higher risk of the first, and certainly the second.

Keep in mind both of these risks are much much lower than so many other things in your house that you do every day. Extension cords, faulty wiring, arcs, heaters, kitchen fires, etc.

I am using Enphase Encharge batteries, which are a LiFePO4 chemistry. They are in my garage, which is heated, so outdoor temperatures don'r make a difference. If they were outdoors, cold temperatures would be a problem below 0F, so if that is your situation I would only do an inside mount. I only have 20-30 cycles so far, but the cycle count is generally well regarded with this chemistry. Still, I don't expect these to last more than 15-20 years.