TBH I don't think the 4cm is really moving the posts here, Treacy would be fine if we had 3 ruckmen go down (however unlikely that is)Jones would actually be an option to play as the number one ruck if all our other rucks are injured though.
Its good to have as long as he develops into a KPF option eventually too.
I don't think Treacy leading the ruck will ever be an option unless we're beyond stacked with KPF depth. Given other clubs will come for our KPF depth if they look AFL standard I can't see that happening - at least not for long anyway.
Plus if Jones is any good as a KPF then he falls under your banner of other clubs coming for KPF Depth, then you rinse/repeat and develop another player anyway