Make OnOpen and OnAttack scripts for the chest that change reputation of faction an make them attack. Use Lilac's Soul Script generator if you can't script on your own.
werelynx thank you twice: first because you answered my question, second because you answere despite I posted, I realized after, in the wrong section.
Anyway I followed your advise and I managed to make the Leader of the faction attacks player when he tries to force the chest, sadly other faction members, that are very close to the leader, wait until player fights against the leader.
It's better than nothing, but not perfect, I tried to change "faction" disposition in the script made with Lilac Script generator, but the result is that above.