From what I nunderstand, constitutionally the federal Government can't charge royalties on a resource - only the states can. Hense the RSPT, a method to get more money to Canberra that is (arguably) constitutional.
So, if you want to stick with royalties and drop the RSPT, then that is exactly what we have now. Royalty rates are set by the states and the revenue goes 100% to the states.
To change this would require a referendum.
I could be wrong but I think that this is correct.
