sounds like a good 6th level ability for a subclass, oh, wait, they removed that, so we now have to wait for potential new subclass with extra attack till 9th level.
Brute subclass:
3rd level: proficiency with all weapons and armor,
no stealth penalty with armor,
sneak attack works with all weapons(this should be default, but hey)
9th(6th) level: extra attack.
You can sneak attack twice per turn, but not on a same target.
13th(10th) level: proficiency in Con and Str saves
17th(14th) level: quick strike, make one weapon attack as a Bonus action.
you can sneak attack 3 times per round.
you can sneak attack same target twice per round.