Re: The AGT Dreadnought Enterprise
I've gotten the impression that Gene always wanted a "balanced" number of nacelles, and this is the only genuine "Roddenberry Rule." But as mentioned, it's a convention that's been ignored more than once. Roddenberry wasn't an engineer by profession, so he never really developed an adequate plot reason for why odd numbers would be unbalanced in the way a helicopter needs torque and counter-torque to fly straight.
"If you think you're brave enough to walk the path of honor, then follow me into the dragon's den."