I think the idea that the ruck position can be filled by anyone - rookies, untalented late draft picks, gorillas - and that we shouldn't spend high draft picks on them, is going to change drastically in the near future. Talented rucks are going to be highly sought after as the position changes from gorilla vs gorilla to tall, athletic midfielder show downs.
The fact is that the Minson types are doomed and if you manage to find someone young like Grundy or Nicholls or Blicavs; that can be effective around stopages, around the ground and in the ruck; then you pay them well and lock them in long term.
I reckon the ruck position will be harder to fill than tall forwards as the game evolves. Best we fill the need while we can.