The two major problems with the system you're suggesting, as far as I can see, are:
1) You don't have any place for TPAs. The NRL has decided TPAs are important as a way of making sure the code of rugby league is as competitive as it can be with external bidders for talent, so they ought to be factored in. What happens if club A's bid for a player is 800k and it comes with 300k of TPAs attached that are, as required, out of the club's hands, and club B's offer is 900k? Is club A required to increase its offer by 100k even though it is already the most lucrative deal on the table? If not, what value do the TPAs have?
2) There's no room for player preference. I have as many doubts as the next person about players "signing for unders to be part of a winning culture" at the Roosters, but equally it's pretty tough to force players to move to clubs they don't want to play for. I'm aware the AFL basically does this but (a) that system is under severe pressure and (b) that code doesn't have the same pressure from cross-code interest. Are you going to try to force a player who doesn't want to leave the ACT to sign for the Warriors even when the response is likely to be taking a contract from the Brumbies? Are you going to tell an 18 year old Indigenous kid from country Queensland that he has to go play for the Bulldogs because they've offered 70k a year more than the Cowboys?