In my opinion PWH is too small to have themed areas, unless they were to only go for about 2 or 3. Look at Pleasure Island, tiny park with 8 themed areas, none of which look that great.
I think one or two key themes could work well. Though I would prefer for the park to go with the current route of creating well themed ride experiences in their own right rather than trying to shoehorn them into a themed area.
The park is too small for multiple themed areas in my opinion - though some more theming between rides would be cool.