If you plan to use this for large-scale access to astronomy I understand. Please note that I cannot do special programming to make a "portal" web site where people can join the network and set up their accounts, and which would do billing etc. You would need to do that. Are you with a University or other educational institution?

If you would be happy simply setting a different priority for each observer/user, and keeping the groups separately on your portal/sign-up system, then I think it could be done. Basically you could re-use the existing Organization field of the Scheduler's Observer records, and put a priority string into there, then I would help you write a script or .NET program that would run periodically and sweep through all of the Plans in the system and force their priority to the value for that user/observer. Thus, if someone uploaded an RTML request with a priority, sometime soon after the task would force their priority to their value.

another thing, it's possible to make a preview image (or last-image) each Project's Plan ?
The web interface already produces a cleaned up PNG file of each acquired image but it only shows the last one. I think you want something for every image taken. Pre-processed? If so I can show you how, in fact the "Customizing ACP" section of ACP Help shows how to add user code to create monochrome "nice" images from the raw FITS for each image taken. This could be expanded to move the nice image somewhere, maybe to a DropBox or ?