Not exactly an experienced premiership winner (let's face it, Wayne and Craig won't be at Brookvale any time soon), but I reckon the best coach without a head coaching role right now is John Morris.
2017 NYC coach of the season after minor premiership finish
2019-20 two from two finals appearances as head coach of Sharks, admirable under trying circumstances considering he was always seen as just an interim.
2022 to halfway 2023 defensive coach of souths - their form during this time defensively speaks for itself. He leaves and they literally collapse.
Tigers defensive coach as of this year, and still early days, but despite the fact that we are talking about the Tigers, I note an improvement in grittiness and defensive resolve (before this round, they were conceding fewer points per game than us).
He's a no nonsense, hard-work kind of man. Had to train, tackle and play harder to compensate for not being the most naturally gifted. Astute, great footy mind, and good with players and big personalities. He has achieved a hell of a lot more than our guy with a lot less.
We need simple and disciplined, with a focus on defence. This is Morris, and the polar opposite of Seibold.
There's my three cents...