Since we already have a holographic crew member who was modeled after a living individual (in The Doctor's case, his creator, which makes sense - who knows more about him than he does?), why couldn't B'Elanna and The Doctor create a holo-Tuvix, to preserve who he was uniquely? Better than out and out obliteration. At least he gets to live on, somehow.
	
		
			
		
		
	
				
			 
				 
 
		 
 
		 
	 
 
		 
	 
 
		 
 
		
 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		