That's one of the options I was considering and that would certainly work, but since I do a lot of RTTY contesting, that would mean operating Win-Test or N1MM over VNC. Today, I found what may be the best solution of all: K4DSP designed a very simple AFSK to FSK converter that could be placed at the remote site. The information, operational theory and schematic are available at:
http://k4dsp.homeip.net/~doug/regenerator/Audio out of the control site computer can be sent down the RemoteRig audio channel and converted to keying closures for the radio, delivering true FSK. For about $10 USD in parts and a couple of hour's work, this seems like a good way to go. I'm surprised a device like this isn't available on the market!
Ron
N6IE