I just recently bought the Director's cut version of Blade Runner and
I realized someting.  If Replicants are like organic robot then
wouldn't that make them something like Thirds?  If so, What if there
was a story where a Blade Runner comes to Mars and is assigned to
retire a specific Third named Naomi Armitage.

It could work.  But keep in mind that Thirds are less organic than 
Replicants, especially the Nexus 6's that put Deckard through Hell.
The only way beyond emotional disfunction that you can spot a Replicant 
is by doing an analysis of their bone marrow.  Thirds have fully 
functional emotions (though each has a unique mental quirk) and bodies 
that are much more mechanical.

Nonetheless, it is an intriguing concept...