Seeing as I was the first person in this thread to bring up the codebase, please hold still while I hit you repeatedly with this large, half-frozen dead carp:
*THWAKK* *THWAKK* *THWAKK*
... because, "code is evil magic" is no part of what I brought up. I brought up the simple, inescapable truth that in order to do this, you would have to have multiple versions of the in-game code. No, not just some art assets, but actual code - the hooks at Trams and the TUNNEL thingie, for example - to allow you to go to Galaxy City. You'd have to have difference in contacts, so that you could be introduced to a Galaxy City contact by an Atlas Park contact, for another example.
Resulting in you now having two versions of the server code to maintain.
And that's just for GC. To add back in ONE single zone.
If you have five different possible changes, mix-and-match-able in all permutations? 2^5 versions of the codebase to maintain. (That's thirty-two, in case you're not good doing exponents in your head.)
...
And what happens if, for example, the dev team updates how the Trains work? Double the versions means double the effort, and thus, double the time.
That is why my response was, and is, and ever shall be: /JRanger