With two guys in Schwarber and Bryant one if whom might have to move to LF I really don't want to see a full time guy signed for the position. That would basically force you to deal an infielder, not out if strength but necessity. Now if Baez doesn't improve fine, Castro probably moves to second in 2016, Russell at SS and Bryant sticks at third but if Baez pans out? Same thing with Schwarber. Say the kid knocks the cover off again in the minors but his catching doesn't impress, another log jam. Now one if these "problems" are probably inevitable but why position block with the likes of a Melky Cabrerra when there are a lot of right handed platoon options to pair with Coghlan?
I don't think you "sign" a full time guy. However, the previously mentioned Bourn makes a lot of sense in trade as giving you the same sort of thing you would be getting with a signing on a shorter term. I've also heard rumblings again of the dodgers wanting to move at least one of Kemp/Crawford/Either. Both the Indians and the Dodgers would make sense for bad contract swaps for Jackson. The dodgers have Kershaw, Greinke, Ryu, and Haren under contract for 2015. They lost Beckett to retirement, Roberto Hernandez to FA, Kevin Correia to FA, and might lose Chad Billingsley to FA($14 mil team option/$3 mil buyout). Jackson is by no means "good" but he's a reliable innings eater that has peripherals that suggest he should have been better the past 2 years.
As a hypothetical example, would Jackson for Carl Crawford + $20 mil be that bad for either side? From the dodgers perspective, they turn Crawford into a position they are likely going to have to address to some extent and open a place for Peterson. They would also save about $20 mil in contract difference. The cubs would be getting rid of Jackson and would basically have Crawford for 3 years $42.25(~$14 mil per). Perhaps you could argue that's a bit pricey but it's short term and Crawford's been worth 2.9 fWAR(469 PAs) and 2.5 fWAR(370 PAs) the past two seasons. Given the 3 years, Bryant's probably still at 3B in 3 years though going farther might not be. Soler is probably your RF. Almora is probably 2 years away best case and more probably 3. Alcantara is going to need some playing time but he's versatile enough to play more of a utility role if they so chose. Schwarber is probably on a similar time frame as Almora.
Crawford is also unlikely to entirely fall off a cliff. If you take Ichiro as a recent corollary, he put up 6.0 fWAR, 4.4 fWAR, and 5.1 fWAR between 33-35. Crawford has more injury concerns but if you hypothetically say 3, 2.5, and 2 fWARs over those seasons you probably get your money out of him and could even potentially deal him to a cash strapped team like say the Royals or Pitt in 2017 if you ate a little bit of his money.