And now I'm thinking of following a similar model for a Twilight 2000 campaign. I would set up the scenarios without assuming the characters will do the right thing or the wrong thing. If they hear cries of help over the radio from a settlement under attack from raiders what will the PCs do? They can ignore it, they can help the settlers, they can help the raiders, or maybe they wait until the battle is over, go mop up whoever is left, and then take the spoils of war for themselves. I'll just let their choices shape the future of the campaign. If they help the settlers, maybe they gain new friends who are able to help out with some food a few months down the road. If they help the raiders, maybe they get some new friends who help them pick some juicy targets in the future. If they defeat both the settlers and the raiders, they get a short term boost to their supplies, weapons, and ammunition.
The thing is, I don't want to punish the player characters for doing the "wrong" thing or necessarily reward them for doing the "right" thing. I just want their actions to have an impact on the flow of the campaign. And and the end of the campaign I'd have an opportunity to tell them the long term impact of their choices. Does that sound like fun?
I've only run a handful of sessions of new Twilight 2000, but here are my impressions, related to what you're discussing here:
-There are some mechanical nudges toward being something less than crazed survivor bandits, but nothing massively overbearing. For example, there's something called Unit Morale, which gives you bonuses to Coolness Under Fire rolls (hugely important), and it goes up and down based on various factors. One of the things that can increase it is helping other people. There's also a great rule about executing people who are incapacitated or helpless--you have to fail an Empathy roll, and even then it gives you a point of Stress (of which you only have a handful, and running out is very bad).
-Also mechanically speaking, it's not like you have levels or magic items to seek out. There's XP-based progression, for sure, but there's no sense of a progression-based finish line you're racing toward. So, if anything, players looking for a power fantasy are pretty likely (imo) to want to set up a compound or similar of their own. That means dealing with friendly NPCs, and interactions that are likely to create bonds.
-Unlike in Fallout, or similar settings where the post-apocalyptic environment is established, the default setting for T2K is basically right after things have fully fallen apart. So there's desperation and scarcity, but things haven't progressed to a full Road Warrior state of depravity and decay. That means you're more likely to come across people who need help. And if you present those people in an honest and vibrant way, I think most players will, like most humans in real life, feel a tug of empathy. In the sessions I ran both players made characters who were defined by being selfish, kill or be killed survivors (reflected in their one-sentence Moral Codes that the game has you come up with during creation). And yet they wound up helping civilians under attack, and later defending them, at great risk to themselves. I think that's the real dramatic punch of the game--do you help other people?
-The encounters and environments that come with the boxed set lean on that central question, in ways that are smart, imo. Like you can draw an encounter card that says a dog shows up, and if you succeed at a Persuasion test it becomes super loyal. If you as a player aren't willing to share some rations with a friendly, loyal dog...well, that's pretty messed up.
-Vehicles are a pain to keep running, and make you a target. So if you're constantly on the move, and just murder-hobo-ing across Poland (or wherever it's set), there's only so much loot you can carry. So, again, being the bandit with the best stuff is a goal that would lose its appeal pretty quickly.
-Finally, this is just my take, but I don't really see T2K being a good long-term, fully open-ended campaign unless PCs discover or come up with some sort of purpose behind survival. Survival might get you through the material that's in the boxed set, as far as the encounter sites and random encounters go, but at some point you'll get across the map or to whatever destination you're after...and then what? There are tons of things you could do as GM to keep things going, including moving to another locale (like making it back to the U.S., if the PCs are from there) and helping to restore order, or fight against those who are using restoration to set up a dictatorship. But whatever direction it takes, I can't imagine things lasting very long if it's just more slitting throats to score another meal. So I think even if PCs start by making nothing but morally "wrong" decisions, the inertia of the campaign will make them true believers in something more interesting.