Your initial statement is invalid. NSW is growing in population and available $. The NSW teams are in reasonable health, if they weren't sustainable they'd be dead. Problems a small number do have are caused by mismanagement rather than lack of demand, and the NRL is working to improve governance as a whole.
So given improved governance and a growing market your assertion that they are unsustainable is at best dubious.
NSW has > 50% of Australia's Rugby League supporting population and dollars.
The only non-NSW team to have proven higher support than any NSW team is Brisbane.
Using other teams as comparison, there is no evidence that a relocated Sydney team would receive more support than they do in Sydney.
The only NSW team under significant stress is the only one not affected by the supposed Sydney log jam.
The failure to significantly improve crowds is an NRL-wide problem which suggests it is a NRL problem, not a Sydney club problem.
The solution to the ratio problem is to increase the number of non-NSW teams, not forcibly reduce the number of NSW teams.
The Sydney situation can be improved by some teams either broadening or better focusing their target regions. St George more Wollongong based, Tigers more Campbeltown based, Manly looking outside the beaches, Roosters and/or Manly taking more games to the Central Coast.
If they are indeed proven unsustainable they will fall behind financially while non-Sydney teams push ahead. Currently this is not happening.