We 3D print the cabinets for our small monitor speakers. Our biggest challenge (other than the time it takes to print) has been with consistent surface finish. If we achieve a nice finish one side then usually the adjacent side isn't the same. All the 3D printed cabinets are now sanded, filled, sanded then painted. Higher resolution printing takes even longer and surface finishing is still required.
I suspect your vents will need to be, at very least, sanded and painted with UV resistant paint. Also, research the different plastic filament that is available. Different companies have standard and unique blends. Check the thermal specs.
Mike