some thoughts

As a manager, becoming completely redundant can only be truly achieved by coaching a replacement. I would advocate in stead of using phrases such as 'useless' or 'corporate fat', to adopt 'retained managerial expertise.'

Finding people who can both manage teams effectively and train new managers are extremely valuable. In larger organizations they would be promoted to 'managers of managers.' Smaller organizations might have no immediate need for such talent, though, those people are crucial if they want to scale. In other words - you should either become a management consultant for small businesses, or help a small business grow.