Server on a boat clone to another server when internet available

Hi.

The client is someone who moved from another company I installed NX Witness and he very much likes and wants the same solution in the new business. 

I have been asked to design a single camera solution for a fleet of fishing boats. These boats will not have Internet until they dock, at which point they will stay powered up for an hour or so.

The main goal however is to have constant access to the recorded footage. So what the client wants is for the boats to backup the footage to another server when they dock. This way they will have everything as soon as the transfer begins, and previous data until then. 

The solution I am considering is installing NX WItness on a Raspberry Pi, then using a linux service like RSYNC to sync the data when Internet is seen, probably via an encrypted tunnel for good measure.

Can I sync the settings, video, meta, etc from one server to another? And how would this affect the web login and licensing? We do not need access from the boat direct. We would like have small virtual machines for each boat that the client connects to after syncs are complete. 

Is there a better way of achieving this?

We wont be able to schedule syncs. I was goinmg to write a script for Rsync to sync when the VPN is active. If the VPN fails mid sync, it should automatically complete syncing files that have not completed sync.