Surely if Qantas were to recommence PER-SIN services with the two daily JQ services already in place, it would make sense to maximise the difference between the two products.
Difficult to see how they can do this with a 737-800. The business seats are "barely business" and not really attractive for a 6 hour flight.
Also the forward galley is small, preventing the installation of an espresso machine and otherwise restricting the range of food and beverages they can offer.
Further back, the 3-3 layout in economy would be annoying on a 6 hour flight because some people will fall asleep, making it difficult for others to get up and go to the toilet.
At least with a 2-4-2 layout no-one is ever more than one seat from an aisle.
I avoid 737s on flights between Perth and the east coast, whether I am flying with QF or VA.
They certainly don't appeal for the longer flight to Singapore.
Of course ANY QFi flights out of PER would be better than none, but I wouldn't want to see them restore the service on terms which doom it to failure.