I think a lot of us are feeling the lack of support for less-than-moral characters. Sure, karma is gone, but I don't really think that's the issue at the core: the game just doesn't support/promote a criminal life style at all. I'll have a few topics incoming, but I think this would be a great first step.
Allow raiders to take over settlements. It's a decently sized task, but one that I think is doable.
First, when Preston announces a new settlement, you can travel there and be approached by a raider when you near it. You can either side with the settlers or raiders at that point. However, this doesn't have to be a permanent choice. Anytime the settlement is flagged for a raider attack or quest, you can choose to side with the raiders if you want. Likewise, Preston can assign quests to you to take back the settlement, which you can side with either party.
Think of the quests! Instead of saving people or taking care of a raider problem, you could get quests to jailbreak someone or kidnap someone. Raider clans are often independent of one another so having non-hostile raiders in your settlement wouldn't necessarily make other raiders friendly (not that a raider is ever friendly). I would also suggest that 1) Raider settlement supply lines are separate from settler supply lines, and 2) Preston is completely oblivious to your actions unless he's an active companion. I can imagine quest turn in could be something like:
Preston: Hey, how did that new settlement come along?
Me: Unfortunately raiders have taken over the settlement and driven off the settlers.
Preston: Damn it! We're never going to get the Commonwealth on our side unless we can show we can protect people.