Realistically there are always some work arounds.
If you know an artist who is adding to the book (signing, sketch, remark) that also cleans and presses books, you could send a Signature Series book through a facilitator to that person. The facilitator would crack that book and send it to them to be worked on, during that time that artist could clean, press, etc, then directly send it back to the facilitator to again maintain the SS Label.
It is all about who is allowed to maintain the chain of custody for the SS program.