Dont think Wayne would turn out to be a 'faceless immortal' even less so that he is working for the set. If there was anytime he have revealed himself it was in obtaining the bands of mourning. Those are about as close to 'end-game' as it could have gotten. I DO however was worried i was only person who had considered this line of though, but i rather believe that he will be MADE into a Kandra. It always seems to be a slightly side character who ends up as a the pivot point in these (sazed, vashar, etc) but rather then the main.
As their are no longer Kandra being made without the Lord Ruler to do so they'd probably only be able to reuse spikes that were already applied to Kandra, so I'm thinking that perhaps he ends up with Lessies -Paalms- spikes. *Foreshadowing moment* When MeLaan said to him "you're wasted as a human". Marsh already set precedent to hold over a character from previous Mistborn group, so why not have another?
Sidenote- the kinda "kandra" in the set? What else do we know that has red eyes in the Cosmere? The Parshendi under Odiums influence (sorry Bavadin)