Hello! It seems like you're requesting an update for the Riverbend Timbers 4x map in FS25 to remove all materials and create a new save for testing purposes. This update will include changes to the terrain that will necessitate starting a new game save.
Removing all materials from the map will likely involve editing the map's XML files to remove or adjust the existing material placements. This process will ensure that when you start a new game save, the materials will not be present.
Additionally, the changes to the terrain will require players to start a new game save in order to experience the updated landscape.
If you have any specific instructions or requirements for how you would like the materials and terrain changes to be handled, please provide them so that the update can be tailored to your preferences. Let me know if you need further assistance with this update!