Could a moving film of gas reduce aerodynamic drag?
No, it doesn't reduce drag through reducing boundary layer speed, but it does create thrust by creating a region of low pressure in front of the vehicle (I mean technically, if the entire vehicle produces thrust, it does reduce vehicle drag, but in either case the reason why that happens isn't because the boundary layer speed is reduced). If you mount the device like in the image, then the low pressure zone will be created. The pressure at the bottom of the vehicle is higher than on the top, so it will generate forward thrust (well, in the orientation of the image, upwards thrust). This is because a jet of fluid will entrain it's surrounding fluid (aka &quot;pull the fluid along with the jet&quot;), which will create a region of low pressure around the jet. There actually are real-life implementations of this concept - 
                
            , 
                
            .
However, the reason why this isn't used in real life is because if it's low efficiency - there's other ways to generate that thrust, such as using a propeller, a turbofan engine, etc, that don't require nearly as much fuel to produce the same thrust.