I wouldn't be planning based on a potential rule change, years down the track. Especially one that is unlikely to come in.
Noddy, Jackson threw Melbourne on his back in a grand final and destroyed the Dogs. There's no better reference. He's done that several times both before and after as a kid, that's unheard of for a teenage tall.
People need to remove the idea that Jackson is just a ruckman from their minds. He's the most athletic tall to enter the AFL, possibly ever. His ceiling is huge and what he could achieve is massive. Even if he gets no where near that, he'll be an incredibly good footballer and is already very good.
As for Ash Johnson, he isn't proven at all. He's played 7 games. Georgiades is an undersized key forward and is shorter than Mundy. He shows glimpses but is contracted and not going anywhere soon. McDonald and Naughton also have long term contracts and aren't moving.
In any case, I've said it a few times but Jackson could play a lot of positions and running around as a midfielder, roving to Darcy is definitely one of them. The sky is the limit with Jackson and he's coming to Freo. Jump on board the kid.