Same here. I have af filter out put directly over the diffusors in my tank, and it is working wonderfully.yes you could. i have the outtake of my filter blowing over a glass diffuser.
What kind of filtration system are you using? I have cannister filter and Quiet1 pump and just introduce CO2 into pump intake where the tube goes out of the tank. Pump impeller "shreds" bubbles quite effectively and pump return circulates effectively.