Hi Bob,
well 2 of the Camera Converters will communicate end to end if you like. How you deal with another headset for a single cameraman or interfacing into your clear com will have to be figured out.
you could use embedded audio over your existing mini converters, using a camera mic channel to talk to control room, and a channel on PGM return for CamOP to hear director. Kind of a thrash but it works.
Or add extra SDI-to-Audio and Audio-to-SDI units on each end of your fiber converters (2 of each required). This is more to the purpose that BMD sort of built their internal talkback around. We built a box like this in the past, works great. Ended up with 2 mics, 2 IFB and 2ch RTS added to the normal 2 fiber camera/monitor setup. This added audio uses SDI channels 13-16, so anything originally on SDI channels 1-12 from the camera or PGM passes thru without modification. The RTS has converters/power units on each end so you just plug one end into RTS, the other end gets a belt pack-its as easy as using a piece of XLR.
Honestly, for a single camera (esp if its a one off show) I'd just run the audio cable. It will work, reliably I might add, and it is the cheapest option by far.
Looking forward, if you do a lot of events of this nature, I would look into something like some of the gear we have built. Systems that handle multiple video paths each way, and either separate audio gear and/or IP infrastructure running on 4 or 6 fiber strands. This way you can drop the fiber box in one location perhaps very far from your control room and use shorter cable runs to spread out cameras/comms/etc. We have a system with 8x 3G-SDI (4in4out) and 5 IP networks and Dante audio supporting up to 256x256 audio if we ever need that much
. 4 fibers (thats just 2 duplex cables). It's all off the shelf gear, with some imagination tying everything together.
Lots of options.