Back when the Zetec was coming in I was totally against it and then 5 years later I swapped my pinto out for a Zetec and loved it. It wasn't because it was faster it was because it allowed me to not have to rebuild the motor every year. Also it was so smooth in comparison to the pinto it didn't shake everything loose.
New motors are inevitable to keep a class healthy for the long term. Also as mentioned before making them equal is much easier with restrictors or map tweeks.
Brian