This is one I've had in my head for awhile, but know I'll never write it, so....

In the original series' universes, from Next Gen on, cloning people has been established, Spock has disappeared on Romulus to work toward Unification, and Kirk has died years ago. So, here's my 'what if?':

What if the Romulan Commander has heard rumors of Spock's mission and decides to lure him from hiding by cloning James Kirk and selling the clone at the Romulans' slave market? The only thing I ask is that Spock be at least 20 years older than when James Kirk died, the cloned Kirk be named 'Kirk James,' Spock tries to rescue Kirk James, and that the clone does not know of the original Kirk.

Other than that, everything is free for the author's interpretation: the clone's age at the sale and at the time of its sentience, whether or not the clone knows he's a clone, Spock's reactions, whether or not the Commander's plan works, whether or not Spock and the clone get together, etc.