Single forest with Single domain.
Current FSMO roles are on one dc in hq. Primary and secondary DNS servers are also on additional domain controllers in HQ. Each site nationally has 2 domain controllers configured as global catalog and DNS.
DataCenter Maintenance in HQ will require complete shutdown of all systems. Systems with failover capability will failover to colocation facility which has 2 domain controllers.
Thoughts on moving fsmo roles out to colocation facility during Datacenter maintenance. Any additional gotchas I have not thought about woul be appreciated!