I am new to all of this, so if I am repeating things you already know about please forgive me.
I am currently on Tatooine in the city Mos Eisley, and once I left the Civic Center, I could not return because the Civic Center could not "hold anymore passengers". I don't remember selecting Tatooine as my start location, but maybe I was hasty in the creation process. In any case the buildings should have a larger capacity, unless of course you think that this would negatively affect the SWC experience. The Civic Center is not the only building that has this problem.
I am not an expert, but does this problem come from characters persisting in a location even if the player is not logged on? I mean, when a person logs off, does the character stay in the last location?
I hope this suggestion will prove to be of use in improving the SWC.
Whatever the capacity of buildings the ones in spawn cities will get filled up so it makes no difference. Elsewhere that will rarely if ever be a problem. In the future the problem will be dealt with however as there is no need for you to go back inside it's not a priority at this time.
Characters always exist where they last were, if you log off you can still be shot at (when we have combat anyway) thus why we have significant time delays.
Very few places will ever be filled up apart from cities where new players spawn and then quit the game. After a year (I think it's a year) those lvl 1 accounts are deleted, however the number of people doing that is consistently high so even when the admin empty them they quickly fill up.
In most cases entities will be filled up due to a bug, the only way it should be possible is if a player chooses to do so, and then they'd have to stay on board so it would be a rare tactic at best. It's also possible the admin would intervene as there currently isn't a way to forcibly remove such an unwanted person using that as an 'attack'.
You can kick people off from the inside easily, however from the outside you can only message players you know are inside and ask them to get off. You can't view the contents of the facility remotely except the basic information provided by an external scan (Number of passengers, number of ships, number of vehicles etc.. inside), no details.
As earlier mentioned, the admin can remove people and in most situations will.