The cost in prospects would be steep--almost certainly Reckling and/or Walden, plus two or three other players. Kendrick might have to be included to allow the Marlins the ability to then trade Uggla. This wouldn't be cherry-picking in any way.
The Miami Herald is reporting that talks between the Marlins and Johnson's agent broke off because the Marlins wouldn't guarantee a 4th year, while Johnson wanted something resembling what Greinke signed with the Royals ($38M/4 yrs), which would buy out the two remaining years of arbitration plus the first two of free agency.
Johnson will be just 26 when Spring Training begins, so a 4 year deal would still be within his prime years, unlike a 5 year deal for Lackey. Johnson had Tommy John surgery in 2007, and this past season represented the beginning of the time when a player is supposed to show the benefits of that procedure. It wasn't just that Johnson was 15-7 last year, but that some of his NDs were heartbreaking; he could have easily won 20 with an offense to support him. Like Kazmir, he saw some high pitch counts by the 6th or 7th innings in many of his starts, but that is often something which fixes itself as the pitcher matures and becomes a smarter player.
At 6'7" and 240, he's an imposing figure standing on the mound. The downside to being that tall is that a small quirk in delivery can make a huge problem in the outcome, so a pitching coach needs constant vigilance to ensure that the mechanics are sound.
Should the Angels make a move to lock up a young talent, knowing it will cost them talent as well? Would he become the cornerstone of a rotation for years to come? Is it smarter to pursue established starters like Halliday and Lackey, whose prime years may largely be gone, or to roll the dice on an impressive young player with huge upside?