This is actually going to be for cgi scripts that are deployed (in the current "old" system) on the same system, so there's no need to act as a full proxy. Theoretically, I *should* be able to just use some aspect of the Apache interface(s) to fire off the CGI script "inline" and then extract the body of the response.
Thanks for the suggestion, though. I'd already thought of proxying it, but that then leaves me needing to have an exposed (in the sense of publicly-visible) cgi interface and I'm explicitly trying to avoid that.