I know there are many assumptions to this question but: Would it be possible to simultaneously configure all area x routers through something like SNMP for the purpose of merging with another area? If this is possible, could someone absorb a multi-area campus network into one area within a few minutes?
The problem is being able to configure routers while you're in transition.
Consider a network with two areas ( 0 and 1). If you change the configuration of the ABR, then all the routers in area 1 will drop their neighbor relationship, and you won't be able to reach them to change their configurations.
It might be possible if you choose the configuration order very carefully, so that you configure the most distant routers first and work your way back. But it's risky, and if you make a mistake, you will have to reconfigure the routers from the local console.