You have to keep in mind here that of the three things a Hybrid does to work its magic...

-Regenerative Braking

-EV Assist to allow for less ICU load (and to allow for the Atkinson cycle without horrible low end torque)

and

-ICE Shutdown at stops,

The third (ICE Shutdown at stops) makes the least impact on fuel economy improvement... unless, of course you let the engine idle for long periods of time.

Being that the A/C being run off of the engine is more efficient than electric A/C (it's also much easier on the electrical system), and given the nightmare of venting an electric A/C unit (which also might cause more wind resistance in the process)... I don't think you're going to save any fuel by trying this out.

You have to keep in mind that ANY air conditioner is going to produce more heat than it removes. Belt-driven automotive A/C systems cope with this by using the condenser mounted in front of the radiator. An electrical A/C unit has the condenser built into it with an electric fan blowing air through it. This would have to be routed through a large hose outside, or it would cause the interior of the car to heat up, not cool off.

An open window with a ventilation hose sticking out of it would not only look more goofy than a Disney character, it would also disrupt the aerodynamics of the vehicle.

One gallon of gas - $3.49

One used four wheel drive SUV that gets 30+ Miles Per Gallon - $15,999

Purchasing it used for $5000 UNDER bluebook because the dealership did not realize it was a hybrid - PRICELESS