Nothing would make me happier than nuclear submarines, because nuclear submarine essentially mean an entire nuclear industry. As a Physicist that one of my personal goals to promote nuclear energy.
Mining, processing, enrichment, reactors for power, military reactors for submarines and other uses etc. To do this there would have to be a massive investment in organisations like ANSTO, CSIRO etc. Your talking about, I dunno say $25 billion and 10 years just in infrastructure, training, education to set it up, then a few civilian nuclear power station to make the whole thing viable (help offset some of the cost). Only after all that could we then think about nuclear subs (costs and operation are additional). I doubt it can be done in a tighter time frame than before we have to start retiring Collins.
Personally I think it should be our priority and where we should be spending our mining profits. Laser enrichment has completely rewritten the game in terms of a nuclear industry making it more efficient, less energy, safer with less waste products. No centrifuges or hideous uranium hexafluoride and truck loads of hydrofluoric acid. As a side effect it would be relatively easy to expand the plant to include isotope refinement for many other uses (semiconductors, solar cells, research, science, medical etc).
With some shiney new nuclear power reactors to add base load capability we could power things like a high speed train network from Newcastle to Canberra. We could also offer cheap power to aluminium smelters and ore processing on the east coast of Australia without spewing carbon emissions everywhere. Forget about a carbon tax if Australia could power its aluminium smelting by carbon free power, we would meet all our harshest kotoyo emission targets.
So apart from fixing a whole bunch of civilian problems it would also be handy for submarines. But its not a quick solution. Requires massive investment. Society as a whole would have to say yes lets do it. With the green hating nuclear as much if not more than coal and old growth logging I don't see it happening in the current climate.