Hm. Double the size of all rooms? Wait, wait. Story behind it could be that V created some kind of demi-plane before his wife succeeded in destroying his phylactery: the mansion. While his original plans were much grander, now it only works like it's bigger on the inside than it looks from the outside.
Otherwise: have the party split (the entrance door is some kind of portal which dumps them individually and randomly--aka GM's whim so as you create two equally strong parties--in different rooms/different but identical versions of the house) and run them individually, regrouping for the final fight which should then take place in a much larger cave/room and increase A's CR and give him underlings (ghast versions of the ones they encounter with Judge I?