I've been trying to add various cards instead of other cards for quite a while as a change to the 'standard' (The Menendian build) build, but I've discovered that the original build really is the most optimal this deck can currently be, without some sweeping changes.  Any small changes are mostly personal preference and don't change how the deck is played much (Grim tutor/Imperial Seal and Inkwell/DSC).  As many people have already stated, it really is the pilot of this deck that makes it incredible, the versatility of the engines allows it to be played well in many matchups.  After a few months, I think I finally have learned how to play this deck so I will be testing it at a local tournament next weekend.