I really like this idea. Personally I use mechjeb to automate tasks that I've already accomplished but are tedious to repeat, e.g. conducting multiple launches to loft space station parts into orbit. As you say something like having the ability to point prograde or retrograde automatically would be a low level unlock, then later on perhaps 'surf' mode, then perhaps the final unlock would be the ability to automatically calculate and execute a Hohmann transfer or similar.