Solution for globally replicated file system

Customer wants to provide its end users (offices in 5 locations spread globally) the possibility to mount volumes on a common file system with the following requirements short list:

• Support for Windows ACLs
• Mountable via NFS & SMB
• Geo-replication of content, for latency reasons
• File locking and Save conflict management
• Support for data/file encryption

MS Distributed File System (DFS) and the upcoming Azure FileSync are being considered, but since the customer is AWS-first, they are turning to us for options.

Any thoughts on proven setups, partner products etc that could provide the customer with a great solution appreciated!