I'm by NO means any kind of expert, but here are my two cents.
I agree with Steve- doesn't hurt to ask Cincinnati Symphony if they
will agree to the recording. Perhaps there is a middle ground, like
they agree that you can audiotape the entire performance, which will
not be reproduced and only a certain amount of the audio will be used
in the film. Perhaps you get some establishing shots of the orchestra
but then the remainder of the scene focuses solely on your performance
and it is like they are not in the room. You could pitch that you
donate the violin to a music school of the orchestra's choice, or sell
the violin on e-bay and give the profits to your director/producer!
Or give it to Doug Block! :)
This sounds like a really interesting arty short film (20-40mins) with
some experimental first person narrative mixed in. I'm sure you could
get a director/producer from ASU or UofA to work with you for a highly
reduced fee. I went to U of A - some great students come out of their
Media Arts program - call Prof. Guilio Scalinger there if you want
some referrals. You could also try the person who manages the student
crew at KUAT in Tucson, as they may be even more doc focused.
Danny Anker, director of MUSIC FROM THE INSIDE OUT may have some
practical advice for you - not sure if he is on D-Word, but here is
his web site: http://www.mftio.com/
The Philadelphia Orchestra was
the subject of his award-winning doc.