Of course the original 737 was built as a short-medium range ship, and I'm sure Boeing thought the wheel doors wouldn't pay off. I doubt anyone would take issue with their KISS approach in 1966.
Today is 42 years later, with the BBJ flying ETOPS several times the original -200 optimum range, & we might argue with Boeing about this. In fact this thread ran rather lengthy in pprune 2-3 years ago. Right now I can't seem to find it.
But commonality is a virtue, too.