I have a question/observation. It struck me when someone mentioned that the doors were modified so that larger ships could fit into spacedock, and then I looked at the starbase model, and noticed that MoonRaker placed more than one door on the base, although only one door is open. Couldn't it be possible, and keep in mind that I am just asking a question and making an observation, that the starbase in ST3 could have had at least 2 entry points, and that both doors weren't necessarily the same size? If, and I say if, this was the case, maybe the spacedoors that the Enterprise used to leave spacedock might have been another set of doors that probably were bigger, which could have allowed the Excelsior to exit the base? Just a thought.
This would also make sense with the fact that if ever a situation arrised, and all the ships either needed to be cleared out so they could get to a safe distance, or to be deployed to defend the base, that a starbase with 2 entrances/exits would be more plausable, since the ships could be launched faster?
Just a thought.