Front end for Emby with site Integration

We currently have a custom website for streaming videos. This site has been around for years and has been upgraded from one different language to another. We are looking to simplify it by using Emby. Emby has user management and APIs to manage users. what we want is a front end where users can select a plan, then process payment using our credit card processor and maybe adding Paypal as well. Then create the account in Emby, and send the user the url with access information. We also need a custom page that the user can access to cancel their subscription which will cancel future credit card charges and disable or delete their account in Emby. In addition we would like to possibly tweak the .css of Emby (which is possible via an API) to match our site a bit more.