Who would you see as a SP that would fit a 4 or 5 year plan like that? Keuchel maybe, Kershaw if he opts out, Corbin (definitely be buying high), but I don't think anyone else fits that bill. There's lots of 1-3 year stopgaps, but that doesn't go through to our competitive window.
In 2020 there's Cole, Gray (depending on your feelings about him), Smyly, Wheeler, Bumgarner, Sale, and possibly others. That's the time to make a spash imo.