Not only that, but line management can change the nature of your relationship with other team members. From being a coworker to setting someone's salary is a big jump. The social and personal impact of this must not be underestimated. As a manager, you are effectively overhead and we have to learn to live with that. You need to make sure anyone considering moving to the management stream understands that.
Some people confuse management with technical leadership or direction.
They need to be disabused of this rapidly. If even the prospect of being the butt of innumerable pointy-haired jokes isn't enough to put him off, you need to identify a role that can help this person expand. Role with it Typically, someone with management aspirations is already a project leader, so extending her range of responsibilities is relatively easy. Unless, of course, she is already banging her head against an existing manager. This might happen when a new team has recently been formed and everyone wants to progress in their careers, but the top folks don't have anywhere to go.