So I am still looking for a way to have a process with root permissions change other processes userids.

No sane operating system will let you do that. Rethink your concept.

So any of the cgi options are not what I am looking for.

Re-read my previous posting. I mentioned FastCGI servers. FastCGI servers and CGI programs share the three letters C, G, and I, but that's all. The ancient CGI spec and the FastCGI spec are two very different things, sharing barely more than the three letters and the idea of having four communication channels (input stream, output stream, error stream, environment variables). The most obvious difference is that programs running under the ancient CGI spec handle exactly one request and exit, whereas FastCGI servers handle as many request as they like, even in parallel, like mod_perl and other webserver plugins. Searching Google for FastCGI would have told you that.

FastCGI servers may be started by the webserver, but they can also be managed by the operating system or daemontools. They can run under every user account you like, each server under a different one if needed. The webserver still can communicate with each of them. PHP can also run as a FastCGI server, or as one FastCGI server per needed user account.

Alexander