You can (can't you??). But you probably should not.
It will make your account vulnerable. (which is why the account gets locked to protect account theft when that is used to recover account)
If you made it now it is not that the question would make it vulnerable. It is that there was a past security breach where the ones at that time were compromised. So a security question in itself is not really making it vulnerable, but the problem is account's that have same security question now as time of breach. It also becomes even harder with inactive accounts as chances of changing security question are none.
So the security question now locks to prevent compromise. It is a pain for those who hit it but it is considered known now, and we really have a LOT less using security questions now then we did say in October of 2015. If you look back there was quite a few more then say today it has went down drastically that more users know it locks account's.