Whoa, I just went through your pics on viczcar, that is quite a project. You're right to be scared of the A pillar and roof rust, those are the most difficult areas to repair. The rest of the cars rust, although time consuming is repairable but the A pillars consist of 3-4 layers of tightly folded metal and there is just no room to work in there. You might seriously consider finding a complete rust free roof/A pillar State side and grafting on to your body.
Any chance that there is an acid dipper in Perth, media blasting is great but will never get into the inner cavities of the subframe. Now I'm all for DIY rust repair, for me it is the process of the project that I enjoy but let me play devils advocate for a second. If you know you're going to spend 35-40k to get this car on the road then that same kind of money will buy you an awfully nice finished Z.
Looking forward to your progress, this forum is great resource for any problems you run into during the rebuild. Will be interested to see what you think of the KlassicFab panels, they look great. Pricey but if they are as good as they look it will be worth it.