1- Would just be a simple plugin to check the group of the barricade and if any of them have been online in past 15 mins, otherwise decrease damage, by 50% or some value we can decide on later
2: Would be a rule not to offline raid, and later on properly plugin controlled. Players would have been on in the past 15 minutes or are currently on (can't log to avoid raid). Would eventually be plugin controlled/enforced.
3: Do Nothing
NOTE: The Result of this is not guaranteed to be instantly implemented, it may take time or be implemented in a different way.