This post by Brian set out some thoughts about Watched/Organised:
To convert an Organised folder to a Watched folder, follow the principles in this post being:
Backup your database
Disable the Organised Folder
Create the new Watched Folder
As you can see from the above post it is undesirable to have two active folders in your library with the same content. That may be less important where it is the same folder but disable/create is the preferred order of events.