Sorry, not sure if this is the correct section i would like to know Can OpenVAS service be made available as-a-Service to our admins colleagues. In short, multiple users should be able to login and do their own vulnerability scans on demand (of their own servers) only.
they should be able to scan other admins servers, only the one they send a request for.

Thank you

Short answer: yes.

GSA is part of GVM and offers a multi-user web-interface where Greenbone implemented a fine-grained permission concept. It is also possible to restrict the target hosts for each user.
GOS 5 / GVM 10 will improve the concept with this feature: