After a PhD in Particle Physics with a decent publication count and citations, I went into industry, where I've been for the last 3 years or so.
I had several motivations for not continuing in academia at the time: some PhD burnout, being unsure of the path I wanted to follow, curiosity about the world outside academia, and other personal reasons. However, after three years in industry I feel that the intellectual freedom and challenge offered by academia is something I miss deeply, and that's ultimately worth more than the money I can make in industry. In addition, I've become more and more interested in certain topics of Pure Mathematics that I'd like to devote more time delving into.
So at the moment I am considering several (not necessarily exclusive) alternatives:
Keep studying in my spare time, and spend a year doing a MSci or similar once (if) I can afford to take a year or two off. Then consider a PhD from there.
Apply for a PhD programme in Pure Math.
Find a researcher or group that would be sympathetic to the situation and start a collaboration with them with views to apply for a postdoc.
Apply for a postdoc in my desired areas directly.
Apply for a postdoc in an area that's not as removed from my previous field (say, Mathematical Physics), and take it from there.
How feasible would these options (or others I haven't considered) are? How could I maximise my chances of success in this situation?