You can use Synology NAS products not only as file storage. The DSM system provides a broad spectrum of additional services via packages – either signed by Synology or provided by third-party communities – the SynoCommunity repository is the most known. The only limitation you have is your NAS hardware platform and its performance. I own DS211 model which reached its End of Sale status already. I run several network services like DNS server there, and I use it as remote storage for SMB and AFP shares as well as for iSCSI LUNs. It also provides some services for my home network and lab. One of them is RADIUS server.
I want to show you how you can use the Synology products as RADIUS server which will use LDAP database for user authentication. This way local accounts that I use for network shares authentication remains separated from any additional accounts dedicated to RADIUS service. Both RADIUS and LDAP runs on the NAS itself.