They should just get rid of the corner three first and see how that works. the majority of threes come from the corner. That way you're not punishing the elite shooters like Steph, but the big stretch 4's will have to incorporate the post up more. We like seeing Steph and trey pull up from deep. But watching bigs camp out in the corner is boring. I'd rather see them battle in the post.
If you want to see more big oriented post up play, it would be better to bring back illegal defense than moving back the 3 point line imo.