Customizing a city or main map poses no issues; it primarily involves making adjustments on the server side. Ultimately, the decision lies with the server owner regarding whether they wish to modify the city or update the appearance of the main town. If an owner desires to change the main town, they have the ability to configure all the NPCs, warps, and other related guides. Everything is adjustable, and creating a new guide depends solely on the owner's willingness to edit the necessary files.
Don't make things complicated, It's really easy to modify xD