@andy.king While the rules I’ve already stated are absolutely true - FOG maintains a great deal of flexibility.
Have a storage group per location, and put one storage node in each group, and make it the master node.
this way, each site can upload to their local master node - as long as the image they are uploading to is assigned to the storage group for that location.
images can also be shared across groups, from master to master - however - this replication is a one-way highway. For example, say we have group A and group B. Each group has one node and it’s the master of it’s respective group. Say you make an image on B and upload. Then say you share that image with group A. The image will replicate to the A group’s master (and then from that master to any other nodes in group A).
But - if you update that image and it uploads to group A, replication will just delete that image and then re-replicate from group B because group B was the original.
These complications and features would only be of use to you if you even wanted to replicate images. If you don’t care about replication, don’t even worry about it. Also - if your WAN link is that slow, maybe you shouldn’t even use replication with fog, maybe you should just sneaker-net the images, or mail them.