Declaring disaster when using a BIG-IP DNS Controller driven disaster recovery data center transition

My one thought is to maybe have a single iRule applied to all the wide IPs, and in the RULE_INIT, declare a global "set Disaster_Declared 0" variable ... then in some DNS-related event (not sure which), check the variable and always return the first pool in the Global Availability pool list if {! Disaster_Declared}. Then, declaring disaster would mean going in and changing the iRule to "set Disaster_Declared 1". Thoughts? If this would work, this seems like fairly trivial iRule coding.