,,,Of course, in real life, this would be something of a problem because the Excelsior
was established as a commonplace background vessel and something of a workhorse, whereas the Sovereign
was a hero vessel and TPTB would thus have been reluctant to "dilute" the heroic value by presenting the newer type in greater numbers or in background roles.
Then again, TOS featured the hero ship type in all sorts of guest and background roles. And the Excelsior
, too, was at one stage considered for a hero role. She was first created to be a villain (which may have directly contributed to her less than flattering "bully" image where the grace of Kirk's ship is replaced by the impression of bulging muscles, a thick neck, etc.). But when Kirk lost his hero ship, the existing detailed Excelsior
model was a natural candidate for his next heroic ride, until different creative decisions were made.