One thing to consider is that the way Ludwick's contract is structured, the Reds don't really save much money by declining his option. The buy-out is large enough that it would only cost around $3 Million to bring Ludwick back for 2015. If he's still reasonably productive and the answer is a rent-a-player it may be Ryan Ludwick himself. If not my picks in order are:
Still think Vidal or Mejias Brean may be ready and better than any of those guys and push Frazier to the OF. Lutz is a dark horse though, but would probably need a platoon partner.
Not seeing it at all with Ryan Lamarre. Looks like the typical light hitting, speedy, decent defensive CF type who are abundant in the minor leagues. Not really excited by his Endy Chavez/Tony Gwynn Jr/Dewayne Wise potential (of course those guys are lefty hitters which is more typical of those 5th OF types).
Winker will take over in 2016 or 2017 IMO. Maybe they keep Ludwick that extra year and go straight to Winker in 2016 and skip all the lesser lights.