Are you creating video links that are to be downloaded to the client’s computer for viewing locally or are you setting up the videos to play inline to the page your clients are viewing? Attaching the video links is really just like attaching many other types of media to WordPress pages and can be done with a wide variety of plugins or add-ons.
The main focus I think is how to best secure the video content itself for your clients.
? Each client needs to be able to create their own login which you will need to be able to attach to a given group that has access to the specific categories where your video content is placed. You will most likely need a couple of plugins to accomplish this goal:
1. User Access Manager
2. Social Access Control
3. Dynamic Widgets
? You will need to possibly exclude these pages from you main navigation which can be done with the Exclude Pages plugin.
Another option you might consider is using WordPress to create your front end, use another application such as PHCDownload
This is a really great free file management application that has support for any file type, user access control as well as pay per access integration. It does take a little bit to understand how things all work together though. You could use a theme for WordPress that lends itself well to iframes and include PHCDownload as an external page that WordPress act as the parent for. Because PHCDownload is php, css and html based you could also create an interface for your customers directly to that application from a navigation selection from WordPress.
Hope this help a little, good luck.