Hang on, you don't need a compliance plate on the car, if it was brought in under the 15 year rule it was not complied and therefore does not need a compliance plate. It also would not have a compliance plate if it is a personal import
Have you talked to the RTA?
Also talk to DOTARS and get a copy of the import approval, that will help convince whoever has to rego it.
I would say though, it is very possible it will require a blueslip. It should not require an engineer's report.
Finally, have a talk to someone like Todd at Japlink and see what they suggest.