Lectern

This custom requirements it's straight forward:
1. You set Permission up that would prevent players from taking up the Quest IF they have it set to "true"
2. You set Message up that would be send whenever player fail to accept the Quest due to that Requirement

And you are done.

Ex:
If you set permission `test.quest.1` and player doesn't have that permission he would be able to accept the Quest quite normal as any other.
But in case of him having the `test.quest.1` permission it would fail to start the Quest for him and it would additionally send the predefined "Message" to him.