I think you're confusing "repackaging content" (as you seem to want) with "providing HTTP proxy services" (as mod_proxy does it). The latter requires a change to the behavior of the client, which in knowing that it wants site A, still asks site B to provide it.

The "repackaging content" strategy is a difficult problem, because you have to rewrite all the URLs of the passed-through content, in whatever form they appear. Otherwise, the browser will end up fetching some stuff directly, possibly confusing everything. For example, URLs in A-HREF elements obviously need rewriting, but did you also consider the Location header for redirects, or cookie domains, or image maps, or even the URLs constructed by Javascript or Java?

It's a difficult problem. I hope you gain enough to recoup the investment in figuring out how to do it. I hope you're also considering the ethical, moral, and legal issues of branding someone else's content as your own.

For a simple start, handling only the A-HREF and Location rewrites, see my column on a poor-man's CGI "proxy".

-- Randal L. Schwartz, Perl hacker