How about have a hefty malus on the LE of -25% exp and money gained from mobs, but can be re-poked at any level. (as someone suggested maybe make it so you need an npc to poke it and it has a cool down)
Makes it so it is still possible to level with your LE in if you really wanted to, but somewhat impractical as it is hampering your progress.
As it can be re-poked when you are high level then those who are trade skill characters can still use it to feel safe when traveling about the city helping others (providing a service).