Those players you listed also came through the grades at their respective clubs. If they went to market, they'd cost a bomb. I'm not suggesting you are saying we should be buying those specific players but my point is this; to afford such wonderful backup, you generally have to get it from within...a player that is happy to play centre or wing because that's what they came through the system as, but are happy to drop back when need be.
The only other way to do it, is to buy a Caleb Atkins (Raiders) or Daine Laurie (Tigers) because they are behind elite talent at other clubs...you get them cheap because they want an opportunity.