Hi,
I'm typically using the AttributeManager in a certain way just before final output, namely adding all needed attributes as new attributes at the top, and setting all input attributes below to "Remove". This makes for a very clear and simple interface to maintain later.
My suggestion is to use this strategy by creating a new AttributeManager transformer that consists of the list with the new attributes to output (as in AttributeCreator), and having it remove all other attributes automatically.
Cheers