To start, 200cfm seems really high. For comparison, I'm familiar with common PC case fans. 140mm/12V is a common selection, and probably millions have gone into their blade design, and as such it's mostly under trade secrets. But those fans top out at a range of about 3000rpm and 80cfm. If you emulate an existing fan design (assuming that they've done the optimization), scaled the fan itself up to 140mm (instead a 140mm frame size), and beefed up the motor to a higher wattage, you may be able to push 200, but the fan would have to run at like 8000+rpm. At that speed, plastic won't handle the load. And then you have to consider how infernally loud that would be. It's within the realm of physical possibility, but just because it can be done, doesn't mean it should be done. I've got ideas on where to start, but I'd like to make sure you weren't set a task with a practically impossible solution.
