Given the way threads go off topic around here anyway I don't see why the NCOP can't be mentioned

NSW hasn't rejected the NCOP out of hand in fact they are still discussing its final make-up. Whether that means the +50mm rule will be part of the final version or not is yet to be determined. Some States are already operating to the Code and as members here are from all over OZ it doesn't hurt to raise any issues that may impact them now or in the future e.g. you move interstate and your vehicle now needs to comply with that States regs or the NCOP does get adopted in your State.
Bias ply tyres ARE legal on modern 4wd's. The ADR's allow it and so does VicRoads for for those who care and they have confirmed this to me. The Police generally don't know the regs that well and there are plenty of people who work in any industry that don't know all about the regs that impact their industry plus there's lots of stuff that gets spread and if repeated often enough gets believed

This particular myth is a point in case and I have yet to see anybody point to the appropriate reg where it is stated that bias ply tyres are illegal.
Swampers are DOT rated but Australia requires a speed rating too but seeing as the tyre sizes being considered here are not going to be Engineered anyway it doesn't really matter.
If you speed limit your vehicle then it is possible to lower the speed rating required.