There actually already is a rule on this, the pitcher has to release the ball within 12 seconds of receiving the ball, as long as the batter is ready to receive the pitch. It's just never enforced. But there has been a lot of talk about possibly starting to enforce this rule, primarily using a visible clock/timer in games - though I think MLB were talking about changing from 12 to 20 seconds if they do start enforcing it.

if you mean that you want them to nerf pitching, I think that the appropriate way to do that is to lower the mound