Transparent proxy with Client side API?

Hi,

I just thought of the possibility to use the client side API with a 
transparent proxy.
What I mean is:
Session between client side API and proxy reads
< CONNECT www:80 HTTP/1.0
<
> HTTP/1.0 200 Connection established
>
< GET /index.html HTTP/1.0
<
> HTTP/1.0 200 OK
> Header follows here
>
> Body

Instead of:
< GET http://www:80/index.html HTTP/1.0
<
> HTTP/1.0 200 OK
> Header follows here
>
> Body

I know that proxies usually dont allow this behaviour, restricting
CONNECT only to the port 443.

How do you think? Seems this to be useful for others too?
Note: As a side effect the proxy wont be able to cache anything.

Ciaou,
  Thomas Kriegelstein

< : this is sent to the socket
> : this is read from the socket