Hi Marco,
At this time, there is no supported method to change/update the base path of a collection.
Generally, you'll want to simply create a new collection if you find that you are wanting a collection with a different base path.
If you have an established collection that you are wanting to point at a different base path, and if that collection has been in use for a while and would be difficult to retire and replace, you might want to consider using a bind mount so that the file system path set for the collection base path points at a different file system location. This can allow you to get around the immutability of the collection base path value.
Does this make sense?