If you read, this is specifically for Military players. It didn't say that, and prolly should. This is the path someoen who joined the military would take, in general.... not all players.
Now, openendedness is good. What's better is having both. Basically, you're profession would be Military -> Navy -> Fighter Jock, or Civilian -> Technical -> Programmer....
Now, professions are the *main* thing you want to do. Inorder to switch, you'd need to meet certain requirements in your stats. Making something your profession will affect a few things, but not your stats. However, all unused stats will degrade over time.
--Chris