@CWO:
Speculating about fictional technology is, as you said, a pretty abstract (though fun) exercise because one’s conclusions can’t be proved objectively one way or the other. Since, however, you’re disappointed by the fact that in the TOS TV series the Enterprise has glowy red nacelle caps but no glowy blue nacelle sides, and that in the first six Trek movies the Enterprise has glowy blue nacelle sides but no glowy red nacelle caps, here’s a speculative argument that might make you feel better.
It is less that I am disappointed and more that I would have rather seen the design aspects of the TOS era applied in a logical retroactive progression when delving into the pre-TOS time period. Star Trek has always prided itself on being based in scientific plausibility or, at the very least, rationale. That includes how its ships are designed. Form fits the function, primarily. This aberration, as I see it, of the nacelles is just an indication that some writers/artists/designers found the need reverse that and make form more important. It was more important to utilize the now-accepted-as-standard blue/red configuration because that is what people thought a Federation starship looked like. As though it would be confusing if this was not adhered to.
As you rightly pointed out, there were probably production/budgetary and technological limitations during the filming of TOS that precluded the use of a more ‘flashy’ ship design. No argument there. However, I do believe that the period from TOS -> Films I-VI -> TNG era saw a design evolution of its own that embodied the natural progression I am alluding to. Designs became more advanced and visually more sleek. Going back in time (pre-TOS) to make a new show while simultaneously having advanced in our time will naturally lead to a more modern aesthetic; it cannot really be helped. The more we discuss, the more pointless I realize my opinions are. Since these things cannot be changed.
Your aviation analogies are well put however.