'since you're all a lot more willing and able to pirate things than I am, I have a question.'
I can't speak for others, but I regard stilling from Id a mortal sin. Of course, when I worked for a major banking industry interest, I did not feel that way at all.
I am curious whether Doom3 uses a hub system as well. However, I suspect that due to the scripting language that is implemented (meaning you script events in an object oriented language internally within the maps) and the global variable usuage of that scripting language, it would be easy to implement hub content.
Here is a good link to this subject.
http://www.doom3world.org/phpbb2/viewtopic.php?t=2625&sid=b36d7f381813df5fbcd3eefb81509520
Also, these guys talk about adding 500,000 poly objects into the maps as if it was nothing, so you may very well be able to put it all on one map.
Cheers