I have been meaning to start a similar thread (The Toby Green Model) for a few weeks now. I agree with you almost completely.
I feel we should have a look at doing "A Toby Green" with Jack. Years ago, before the GWS midfield became super stacked, Green was there best young mid by far. Racking it up in a team get smashed week in week out. Over time they acculimalted a gluttony of elite mids and they were forced to adjust. Just like we are now. Over the course of a few seasons Green went from one of GWSs excess mids to a AA level small/mid sized forward.
Green still attendants center bounces and rotates through the midfield but his core role is a goal kicking, hard edged competitive forward. I cant see a reason why Jack cannot emulate a similar reinvention of himself as a player. His set shot goal kicking is actually very good, hes ability to bust tackles and snap the ball is also elite. He break tackles from guys much much larger than him, so the small defenders are going to have a real rough time lining up against him and holding him down. The biggest weakness or attribute he is missing is the ability to compete overhead.
Moving jack forward for the majority of game time allows Gus to play his natural role and Oliver/Trac can all rotate with Jack when ever they need a rest or we need to mix it up in the center. This of course may all fall in a heap if jack is unable to perform up forward however I don't see a downside of giving it a crack for the rest of this year to see if we can't improve overall as a team. I'm not saying Jack will become as good a forward as Green but I can see him kicking 30-40 goals a year and also extended his playing career much longer.
Additionally to Viney going forward I would push Tmac back to CHB were he can find form and releases Lever to roam a bit more. I feel Tmac is a much better defender then Tommo who should be running up and down the wing as we recruited him to .
My best hypothetical 22 would be:
Lever - May - Rivers
Hibberd - Tmac - Salem
Langdon - Oliver - Tommo
Fritch - Jackson - Melk
Pickett - Wied - Viney
Gawn - Gus - Petracca
INT - Harmes - Hannan - Spargo - Sparrow
I feel this straightens us up and really allows the players to play roles they are suited for.