Upload & Sell: Off
Tell that to the companies that are already doing it. There are probably 3 or 4 available, today albeit Pentax did it for a smaller sensor.
Ok, but the 40 2.8 STM is pancake light. You get get two of them for the weight and price of an Ultron 40.
As I said before, people wishing for a 40mm f/2 from Canon, wish for another lens. You cannot say that you want "this lens" to be faster.