Nuadu
Seems to me that regardless of what happens in the book, this character makes a useful big bad for the show. Heck, if he can come back once, who's to say he can't come back again in a way that Bob hasn't thought of?
Let's put it this way - keeping a good villain down is always hard to do. How many times did Frankenstein rise, pheonix-like, from the flames? How many times has the Doctor finally destroyed the Master only to have him impossibly return?
Uncle justin was established from the start as the Number One bad guy for this series. If he was as cunning and full of foresight as to have created one doppleganger in the event of his possible demise, I am sure he wasn't so foolish as to make just one. Had there been a Season Two or even Three (sigh...would that there was), I guarantee he would have made one or more returns to cause trouble.