Isn't this what you were hoping to achieve?
One setting per Tag on how much reputation a user requires before being able to do something with it?
You would need to to add this setting to the EditTagModal I think.
public function reply(User $actor, Discussion $discussion)
{
if($discussion->tags->first(function (Tag $tag) use ($actor) {
return $tag->justoverclock_reputation_required > $actor->justoverclock_reputation;
})) {
return $this->deny();
}
}