I just gave it another go based on what you have here. However I think I still have a doubletag in place. That is where my other concern came into place. When you create a multipolygon, you are essentially create a new area. However I can't seem to find a location to add the "outer" to that new main location. 

I can only add it to the original. However if I have 2 natural=wood then it would be double tagged. 

I did give it a go and I will see what happens. Maybe you can give it a once over. 

Thank you for the help!