thanks for your question and welcome to the Rebex forum.
Yes, the scenario you have described is supported.
Your new database-based file system provider will inherit from the ReadWriteFileSystemProvider abstract class.
Actually, we also have heavily commented samples (unreleased beta) that demonstrate how to create a database provider using the:
1) Entity Framework (EF) 5 Core.
2) Entity Framework 6. (for 'old' .NET Framework).
If you are interested, please drop an email to email@example.com, and I will send you the link to the sample. Or let me know in a comment that it is OK to send you the link to the email you have in the forum profile.
More info about Rebex virtual file system.