ProxyTimeout using mod_rewrite proxy?

Hi. Hopefully this isn't too off-scope for this list. We want to =
implement the ProxyTimeout directive with the proxy facilities of =
mod_rewrite, not mod_proxy. We wish to have:

RewriteRule ^/http/(.*) http://$1 [P]
RewriteRule ^/https/(.*) https://$1 [P]

but including a 60 second proxy timeout on these due to an unreliable =
app server at the proxied destination. Is this in anyway possible?

Many thanks, Nick.