The apartment building should have proper equipment to mitigate the risk, and one has the right to know it's there, or find another apartment building better suited to their concerns.
Then we should be outlawing the act of messing with a battery pack in an environment that cannot handle a disaster. Giving companies a pass to make non-repairable junk and/or charge an arm and a leg to repair or replace components is completely unnecessary and contrary to what a healthy society needs.
I don't doubt at all that you are already liable in that situation. But that doesn't mean that it is a good idea to do this. Most people that start on a project like this will have absolutely no idea of how dangerous this is. They will see the 18650's and will make all kinds of assumptions based on their experience with other batteries that have nearly the same form factor (say AA's) and think that this is equally dangerous.
