I think if they go biggish on a starting pitcher they should probably trade Ranger though, unless they are somehow able to unload Walker at 50%.
I don't think you can build a team to win the World Series. You build a team to win the division, or you don't. Both approaches are proven to work as far as getting you to the World Series, even if this year the two best regular season teams got there.
But the Phillies can't necessarily expect to win 95-100 games running it back both on their own merits and because the competion will be better. So if the goal is to be better than last year, yeah, they need to change it up. But if they also want to just be good enough to make the playoffs and then see what should be done in July, that's valid too.
But, our owner and GM's temperament, and the money, and the competitive window for this group, suggest they will be aggressive.