I just think in the modern NBA you have to have good wings who can play both sides of the ball and in the West you have to have a great PG. PF is probably the least important position as centers have gotten way more important.
So that's why in another thread I'd suggested trading Blake for Jimmy Butler. I think they could really challenge the Spurs with a crew of CP3, Butler and DeAndre. Good blend of experience and youth, attacking and defense.