Wesley is no where near as good as Tre right now. Blake has made good progress, but is still very much a work in progress. He at least looks like an NBA player currently and is playing some solid defense. Blake has a much higher ceiling than Tre, but he's no where near overtaking Tre just yet, and Tre Jones isn't a starting caliber pg. I hope that Blake continues his improvement and I hope that he becomes a solid rotation player in the NBA. That would be a success for him. Anything beyond that would be gravy.
There's zero reason to start him until he plays extremely well with the 2nd unit.