You can do that right now with the existing features in core, so that covers.
The other piece you want is
For this you could use either user notes as suggested above, or another custom user field where you could just type in whatever you wanted. Or, if the process is predictable, you could have another dropdown with stuff like
- contacted user/waiting for reply
- approved
- denied
So I think that might be all you need and you can recategorize as Support?