I'd run for governor or be a lawyer. My favorite part of software engineering has been systems thinking and either of those professions give you ample opportunity to design and explore systems. (I wanted to be a lawyer in college but the Great Recession -- and an astoundingly high number of lawyers saying it's a terrible idea to become a lawyer -- scuttled that idea. Software engineering exercises the same *STJ personality type proclivity for rules and systems.)

And I know it's not a "career" but being a gentleman scholar would be even more fun...