Backup Exec: EC2 and On-Premises CAS/MBES configuration

We are working with a client who wants to move all his on-premises infrastructure to AWS cloud. There is a limitation with his WAS bandwidth which is 1gb. Their total data size is 30TB. Since the data size is big and the WAN bandwidth is limited they are going with a transportable disk which will take the initial full back to the cloud and then there will be just incremental backups that will be sent to cloud.

My query is has anyone done a configuration where there is a CAS and an MBES on EC2 virtual machines and then there is another MBES which is on premises. Can we have some pointers on how we can achieve this setup. How will the communication between the CAS Backup Exec server on the EC2 and the on-premises MBES server happen? What are VPN configurations that need to be done to get this configurations working.

I believe that if the communications between all the servers is working, then this setup should work and the customer can achieve what he is looking for.

Any pointers regarding this will help a lot.

Thanks in advance!