I think it is hard to separate service time and team control when considering a trade. I would put Arcia clearly 4th, and the other three could probably go in any order. Dickerson, even with inflated home numbers, probably has most bat now, Rosario has the all around game, and Kepler has the upside. I agree with your last point that a trade is probably in order, but I am really hesitant to trade 6 years of control of a good young player for 2 years of a reliever. I don't value relievers that highly. If I'm trading Rosario or Kepler, I want a comparably young solid starter, or a couple of years of a really good starter or maybe a (half) year of an elite starter if that is putting the team over the top (and same for other everyday positions). A reliever doesn't do that, perhaps moreso in the case of McGee because he still has elbow questions.