To anyone interested I recommend reading this thread as it has a lot of information regarding modding the ETW map.
http://www.twcenter.net/forums/showthread.php?355187-Guide-to-the-ETW-map
Regarding adding new campaign buildings (settlements, towns, ports, farms, and resources) I have the following advice.
- The campaign buildings must be added to the DB tables, regions.esf, and startpos.esf. If they're only in the first two they won't appear on the map.
- If a campaign buildings is not in the pathfinding.esf when trying to enter this building the unit will teleport to this building from anywhere on the map but won't be able to leave. Unfortunately it's not possible to edit the pathfinding.esf without special tools.
- Some Russian modders found that they could solve the pathfinding bug by building a fort, making a hybrid startpos, then coding a campaign building where the fort was located. This works because the hybrid startpos has a pathfinding entry where the fort is located, so if you keep the fort's pathfinding information but put a campaign building at these coordinates the pathfinding bug doesn't occur.
So if you want to add a new campaign building I recommend first getting it to appear on the map, then update the pathfinding information. This is so that if you make an error with the campaign building it's easier to detect.