@OP
I'll humor you & pretend this is legit.

So...you want to be able to join low level dungeons & stomp everything?
Now lets say they removed this restriction...

You'd now be complaining that no one knows anything about their Jobs.
Why? Because the majority would get powerleveled by their Free Companies.

Folks would jump from 1 to 50 in a day or 2. They'd have no skill, no situational awareness, no knowledge of rotations, and no idea how their Job plays.

That said...I will agree on 1 thing. The EQ2 Mentor system would be nice for this game.

Just remember...all Mentoring did...was sync you to their level, give the mentored player some bonus xp, and heavily nerf your abilities. You were NOT powerful, you only had to option on unmentoring when the shit hit the fan to trivalize content.