In order to successfully give the Knock Off treatment to Smack Down, you'd have to bump its starting power to 75 or 80.
And even then, it's not like you were switching in Flying-types to check Rock when you could just send in a Steel or Fighting-type to blow them the fuck away. You'd probably wind up buffing Fighting-types more than anything.
>>21080581>Buffing smack down in such a way could give a lot of pokemon another coverage option>coverage optionNigga.
Why.
Rock as a coverage type is fine. It needs no changes there.
Rock as a STAB, however, is worse off than pretty much every other type. I'd honestly rather we left the existing Rock moves alone and made a new Rock move for Rock-types and not another fantastic coverage move for Ground and Fighting and Steel types that's too unreliable to serve as a spammable STAB.