Having changed your role since the job was advertised, and the fact you don't have the extra requirement for the shortage list, will almost certainly mean your job will have to be readvertised. Sorry to hear that.
Otherwise, if your boss can convince people that nobody else is better suited than you, the higher level job would probably make the application go through quite smoothly.
Aha - a further thought occurs to me. If you apply for residence under SMC
https://www.immigration.govt.nz/new-...-visa#criteria, and get your Invitation To Apply, and THEN apply for your Essential Skills visa (to cover you while you wait for the Residence visa to be processed), you would be exempt from the labour market test. See here, WK3.20.10.
https://www.immigration.govt.nz/opsmanual/#66937.htm I realize this probably sounds a whole step more complicated, but it would actually cancel out the difficulty you well might have if your job is advertised, and there are other suitable candidates - INZ are very strict about employers taking NZers or NZ residents in preference to a foreigner who would need a new work visa.