I've house-ruled Grappler so that, in addition to advantage on all Grappling related checks, Grapplers can
1) do 1d4+str dmg on a 'shove' (reskinned as a throw/slam/hard takedown, etc.)
2) Attempt to strangle an enemy. Grapplers must first roll to immobilize (restrain) the enemy, then pass three consecutive Grapple checks. Strangled enemy is brought to 0hp rendered unconscious. Killed, if Grappler maintains the choke for another round.
3) Attempt to cripple an enemy. Grappler must first roll to restrain an enemy, then must make a contested Athletics check to attack a limb. Success means the enemy takes 1d4 + str dmg and is under some sort of crippling effect (only one arm can be used, disadvantage on physical attacks, -10' of movement, etc.)