Smart File Subscriptions

I have just started using File Subscriptions with Collaborator. It doesn't quite do what I want it to do however and I was wondering if there was way to do it.

I would like to set up a File Subscription such that any changes to a project's code file automatically adds me as an observer to the review if I am not set as a reviewer. I thought that setting this up would be simply to use something akin to the following:

Files Pattern: //project-root/**/*.file-ext

My Role: Observer

This does correctly add me as an observer to all the reviews I'd like to be on. 

The problem is that authors can no longer add me as a reviewer to their reviews as collaborator adds me in as an observer and prevents them from changing my role on the review.

Is there a way to achieve this? Ideally collaborator would automatically add me to matching reviews as an observer, but would allow authors to change the role to reviewer if they wished.