After several years as a post-doc I am facing a similar choice.
If I understand correctly you have no research experience so far. I'd strongly suggest completing a doctorate because:
You may also be able to continue as a post-doc with almost the same freedom. I have done this for 5 years. It cannot last forever, though, and the longer you go on, the more people will expect you to devote yourself to grant applications, teaching and management. That is why I'm quitting.
once you have a doctorate and some publications, it probably won't be hard to persuade a professor to offer you an honorary (unpaid) position which gives you an institutional affiliation, library access, and maybe even a desk. Then you can go ahead with freelancing, without most of the disadvantages you cite.
Huh. That's a fascinating idea, one which had never occurred to me. I'll have to give this suggestion serious consideration.
Ideally, I'd like to save the world. One way to do that involves contributing academic research, which raises the question of what's the most effective way of doing that.
The traditional wisdom says if you want to do research, you should get a job in a university. But for the most part the system seems to be set up so that you first spend a long time working for someone else and research their ideas, after which you can lead your own group, but then most of your time will be spent on applying for grants and other administrative trivia rather than actually researching the interesting stuff. Also, in Finland at least, all professors need to also spend time doing teaching, so that's another time sink.
I suspect I would have more time to actually dedicate on research, and I could get doing it quicker, if I took a part-time job and did the research in my spare time. E.g. the recommended rates for a freelance journalist in Finland would allow me to spend a week each month doing work and three weeks doing research, of course assuming that I can pull off the freelance journalism part.
What (dis)advantages does this have compared to the traditional model?
Some advantages:
Some disadvantages:
EDIT: Note that while I certainly do appreciate comments specific to my situation, I posted this over at LW and not Discussion because I was hoping the discussion would also be useful for others who might be considering an academic path. So feel free to also provide commentary that's US-specific, say.