Start all new jobs at lvl 30 or introduce new pre-requisite classes for them at lvl 1

[Seraphor]

Meh, they don't have to be 30 but I would be in favour of certain prerequisites being met.

Dark Knight requires a Gladiator or Marauder at level 30.
Gunbreaker requires a Paladin, Warrior or Dark Knight at level 60.

That sort of thing, you'd need at least a general understanding of the role you're going to play before you can dive straight in at level 50+.

Except you can buy jump potions, so the field isn't level.

[Jandor]

Except you can buy jump potions, so the field isn't level.

Do you reckon that's the route the majority of people would go?

[Seraphor]

Do you reckon that's the route the majority of people would go?

Well it would probably encourage more people to go that route. But the point is, if you can bypass that requirement, then enforcing it on non-cash-shopper in an effort to make people learn is a bit futile and kinda petty.