I agree that they are morphing into Tiger even down to the elderly 737s. The problem is Jetstar, Qantas and Virgin are all aggressively competing now on leisure routes so a lot of the Tiger share may have already gone unless REX is prepared to take themselves down-market and become a true ULCC positioned below Jetstar.
This would mean they will be more like Spirit in the US, or Ryanair in Europe with a very no-frills operation. The virtually pointless existing J class offering would be removed and the density increased to a 28" pitch. Gates leased from airports would also change with no airbridges required. They would need to gird their loins to withstand the inevitable ACA segment complaining that nothing is included and delays are not recompensed with accommodation, meal vouchers etc even though this was clearly stated when the ultra-cheap ticket was sold.