File backup to complement Veeam

Consider the following usecase:

VMware ESXi 5.5u2 with a Windows 2012 R2 fileserver VM with 2 x 3.6 TB datastores.
Data mostly consists of large CAD drawings and loads of smaller .txt files.

Currently being backup on the VM level with Veeam to a NAS repository - which works without issues.
However due this being a fileserver the client wants multiple revisions of files and longer retention periods aswell as two different backup products for security reasons and as such we are looking for a file level backup product to complement Veeam.

We have been conducting trials with different products which all does local backups to NAS, such asCloudberry server backup, Shadowprotect and other less known products but was interested in hearing suggestions and feedback from the community.

So would love to hear suggestions on a file level backup product...