I've been known to display astromechs twice if they're listed as being seen in multiple places. Like one on the streets of Mos Eisley that showed up in the rebel hangar or some such...
I display multiples of army builders almost routinely. 2 Royal Guards flanking Palpatine for instance, as I have none of my outrageous armies displayed but a double-up is cool.
I was just writing up my Veers digs actually and while I really actually loathe the Veers figure in several levels, I do think there's some justification for displaying two if that's your gig.
Same with the Gonk droid... In the hangar he's got a very similar version of himself behind him sans head port things. He could be bought a 2nd time and displayed without his attachments and look pretty spiffy.
C-3PO Removable Limbs could be built and also in the bag riding on Chewbacca...
Do the 3 head variants of the Fleet Trooper and Imp Officer count too?
Or the Blue & Brown coat Han Solo Hoth figures?
OOOOOOooo Blue/Brown debate... That brings back some good memories.