"Fragment" request header

Is there any interest in adding a "Fragment" request header to expose that
part of the request URI to the server? It seems useful as an optimization,
and to keep "#!/" AJAX links from breaking.

Such a header would seem to be backward compatible, and could be reflected
in the "Vary" response header. It could even be an opt-in feature if
signaled in the TLS handshake.

thanks,
Rob