http to http without a 30x redirect?

So if I understand you correctly, you wish to send traffic to two different pools. Where one pool uses HTTP servers and the other pool uses HTTPS servers? So based on the URI the BIG-IP virtual server it can serve both websites originating from either HTTP or HTTPS, while the client continues to stay connected to the same virtual server talking for example HTTP?

Maybe this piece of code helps you going:

when CLIENT_ACCEPTED {
    SSL::disable serverside
}

when HTTP_REQUEST {
    if { [HTTP::uri] starts_with "/Fwoosh/" } {
        set uri [string range [HTTP::uri] 8 end]
        HTTP::header replace "Host" ""
        HTTP::uri "/Bar/$uri"
        LB::detach
        SSL::enable serverside
        pool some_https_pool
    }
}

Your VS will need a default_pool (HTTP) and an attached serverssl profile.