Lynn turned 30 in May, Cobb this October. Neither has a great track record of durability, they are both short-run fixes where you cross your fingers.
Darvish will be 32.
Aren't a lot of spring chickens in free agency. Basically, it's a win now move.
Yelich had a big year in 2016, regressed back in 2017, basically he's a 4 WAR player, which is solid, but not a huge upgrade. OF is not the weak spot of this team, now or in the future.
Stanton is a gamble on health given his contract, when he plays every day he's extremely valuable, but he's been hurt most of his career.
There's just no slam dunk answers out there.