we looked into it and found only a SQL trigger would work. Our two options appeared to be base our groups' dynamic queries on a custom property whose drop down list we managed (as Orion admins knew to create groups when adding new values) or just create a query to keep up with what engineers selected.
Did the later with a custom query which showed me any nodes not already in a group and posted that right on the homepage.
With that its easy to see when a node has a custom property which is null or does not line up with a group dynamic query.
Let me know if you want the SWQL...
