If enabled in Globals, clients can request custom-built dedicated servers by simply clicking a link. When they do so, a trouble ticket is generated:
When you receive such requests, add non-templated servers and assign them to users by changing server's status to In use.
In your TT system, you receive requests for custom-built servers both from clients with your servers and from clients with your provider's ones. Forward the latter to your provider specifying the server details and id of the client who sent the request.