I go another way, giving more offensive power. Unarmed strike damage increases as follows: 2d4 dmg at 4th, 2d6 at 8th, 2d8 at 12th, 2d10 at 16th and 2d12 at 20th.
At 10th level, also allow any 1's or 2's on intial rolls to be re-rolled once, like Great Weapon fighting technique.
This balances...