To be honest, I don't think I have the right background to do any of the things you mentioned. I have a math degree, but it's just undergrad and I have barely used it for the past decade. However, both Jane Street and Two Sigma (moreso) advertise a number of purely development related positions. This is the sort of thing I think I'd be applying for.
Sadly, this is probably classified as "IT work", as derided by Wilmott.com forum users. I don't really care, it's the same sort of thing I do now. I just wonder if I could get paid more doing it for a prop firm vs. an "internet" company. I'd love to learn more and move into another role, but I would have to start with what I know.