User Sign up and MAC authentication

I’ll try to be brief with this.

Currently, we have a customer ‘walled-garden’ in place where a user enters their account number and pin. It authenticates to a mongoDB to verity they are active and then utilizes the Mikrotik API to create the user on the Mikrotik and activate the host.

We are looking into implementing Radius/Usermanager for more user accounting and better centralized management. However, we really like MAC authentication and the automated sign up process so we aren’t having to constantly update MAC addresses when a user buys a new router or we swap one out.

So, my question is this. have any of you done anything like this where you use MAC authentication with UserManager or another flavor of Radius and had a sign up/sign in page to authorize the MAC for the first time?