[thedrbrian]

Another problem is how planes are designed for different sizes. Say you design your plane with the base / most ordered as the dash 9. Now someone wants a smaller longer range one.

just take some fuselage barrel sections out. Boom dash 8. Want an even smaller one. Take more sections out. Dash 7. Need a huge massive super long range one with loads of seats. Add sections and you get the dash 10 or 11.

Current planes use a uniform fuselage structure for this reason. You're going to make different models within the same model family with a flying wing.