Provide clean memory on each request, so that dirty CGI scripts would also run
I think that is just what makes mod_perl so fast and mod_cgi so slow. Because you don't have to reload/re-compile the scripts every request, you get the speed-up. I do not know of a way to keep the compiled code around (other than turning it into an *.exe file) after having it run but still provide a clean slate of variables and state each time it runs again. It's an interesting idea though and perhaps worthwhile of further research.
"If you have four groups working on a compiler, you'll get a 4-pass compiler." - Conway's Law