I have been working with major networks for some 29 years in Post Audio and in Video editing. You claim that the work flow is long with FCP to Protools. I too have that set up and it is just a few seconds. I have a Protools HD rig and a FCP studio 2 setup and I find it very easy to go from FCP to PT then back with a final mix to FCP to lay it off to a tape or a video file. You do not have to be picture lock either.
The pluses to having an engineer work on your project is huge, their creativity, knowledge can make your project go from good to fantastic in a heartbeat. The audio that I receive from the field on pieces is absolutely horrible these days. The DP thinks that he can record audio and direct a shoot and not have to worry about the audio levels etc…I am asked a lot of times to please fix my audio..I never heard that in my edit..Where did that come from? THese are statements that I receive from my clients and others that I am trying to help out. I just took a piece that was recorded in the field at it was so low and close to the noise floor that it was extremely hard to even hear the talent. With my experience I was able to get it sound very good and it aired on natioanal tv.
I would suggest that you use a FCP rough mix for approvals, but for the final I would have it go through a engineer, using a DAW like Protools, Logic etc…