[Question] Map connections change through event??

I'm making a fire red ROM hack and I'm trying to create an event that will happen after a certain point where one of the main towns is on fire or burned down completely. I want to just make a clone of that town and then adjust the tiles accordingly and when the event triggers to show the new town the game will change the map connections from the routes connecting to the town to be to the new town. I have no idea how to do this and I haven't been able to find any information to see if it's even possible.

Does any one know a way of doing this? Or is there a better way to handle this?