Can someone with a Ph.D in field X get a job in academia or industry in field Y, even if the job posting says "PhD in field Y required?". If not how will going back to get a second post graduate degree be looked upon by academic and industry employers in field Y?
Background:
I am finishing my PhD in Mathematics and am currently on the job market. Ideally, I would land a math post-doc position, however, I have also been looking at industry jobs (as some of these would be more satisfactory than say a 4/4 teaching load or 3/3 or whatever it would be), but most of these seem to indicate that I would need a M.S. or PhD in Computer Science.I have a background in math as well as in C.S. (B.S. in C.S., B.A. in Math).
If I don't get a post doc offer, I am considering attending a school for a master's in C.S. in machine learning or a related field. Considering I have all the math background, I believe I would be a good candidate for a M.S. or PhD in C.S. And there are a lot of interesting problems where the two areas overlap.
Is it reasonable to return for a second degree if I don't get my dream post-doc offers, especially to make myself more marketable to industry? I am seriously considering this option.