As a temporary workaround while they work on this, you can build a segmentation based on states and countries and which time zone they fall into, and then add the send and wait steps in a template.
Instead using multiple campaigns you can define in the Flow using the wait steps & add choice of a single campaign, if you are running a single content at the time.
Hey Andy, This is an awesome solution! Do you mind sharing the smart list logic for your GMT segmentation? Do you have a "Timezone" field? Did you use tables from something like Data.com or another website? My team loves this idea and we'd love to get it implemented ASAP. Any help/insight you can give us would be much appreciated!