Imagine having done nine tackles, only for Liam Moore to then yell "10 again!"

Well ,for a start you get rid of the six again rule which is difficult for spectators to follow & go back to a penalty kick.

Radical, but the fatigue of the defensive side has to be considered, and 6 again (or 10 again) rule on to of 10 tackles.
Not so sure it would benefit the game or player welfare having a team defend 16 or 20 tackles or more in a row.

I'd like to see this. The penalty for holding down is far more severe when the opposing side gets either a 25 yard punt to touch and 6 more tackles from an ordered start or a chance of 2 points.

Right now sides have very little penalty for holding down early in the tackle count, almost encouraging it, and it's ruining the spectacle of the game.