converting air con flap actuators?

recently had a sticking motor (or possibly the green arm) on the defroster flap actuator, and i also have another actuator that has never worked since i bought the car (never get air out of the three central dash face vents). i was looking at replacing both with second hand units, but the defroster flap actuators seem to be quite rare, so wondered if it was possible to convert one type to the other by swapping the arm linkages over etc? i realise this may involve some level of disassembly, but the internals seem reasonably simple, so wondered if anyone has successfully converted a flap actuator?

I have a stuck flap which I have left open to ensure that the demister works whilst considering the best solution.I don't want to lose the demister suddenly again so might buy new if as I believe they have revised the servo to make more reliable,Dont know if they are interchangeable but seems risky