Hi Linda,
There is at least one Product Idea here in the Community that relate to your use case of Revise only when the Object is part of a Change and I encourage you to vote it up. http://communities.ptc.com/ideas/2974
As far as User Revise on Released Objects, you probably need to enable this permission through access policy. What you can do though is establish a "rule" that undoing unwanted Revisions must come through your manager rather than users going to admin directly.
I don't know of any way that would put this restriction in place but pretty much anything is possible with Customization.
As far as the create Change Notice workflow assigned activity you can make a couple of adjustments in the Workflow. Change the participant to another Role (you could assign a specific User here but not the best idea... (just because you can does not always mean you should). The User would need to be in the Role for the Context Team and you can set permission to create a Change Notice (and don't forget to also set permissions for Change Tasks) in the Policy Administrator. If your concerned about your "heavy user" creating Change Notices without authorization there is also a Preference that determines if Change Notices can be created without a Change Request
You can also change the workflow assigned activity for Change Request approval to be a Set Up Participants type to allow the approver to set downstream participation to save reassigning.