It would be a good idea. Being a saboteur player killer (like the most current players of 3.x) should turn you into a target to the rest of people, not encouraging your ego even when game logics says that you’re on a negative reputation, lol.
The problem with this theme and the whole survival in general is that most players do PvP for merely fun out of boredom, or simply being childish happy triggers, rather than for gameplay-wise purposes. Overhauling survival and PvE aspects, including making zombies stronger, would help a bit to fix that up.
In the case of reputation system, I think it would be better if there are NPC factions that you may keep a reputation with, to obtain good worth-seeking benefits and safe zones in case of extreme distress, and not just a global set of reputation that either determines if youre “nice” or “mean”.
So you may lose reputation for one or maybe two of these factions in a single map if you’re a happy trigger and go all around killing everyone just because, causing these factions to deny their benefits to you and even shoot you on sight if you approach to them.
As it seems to be intended, survival in 4.x won’t be as easy, and player capabilities won’t be as OP as these are in 3.x, making any help to survive a good chance to stay alive and an incentive to make your choices considering multiple aspects than just selfish dumb fun (this is not CoD, for f*cks sake).
In 4.x, I see PvP as a more gameplay-wise action when you’ve already settled up with a large group of partners, as you’re almost forced to cooperate with others to survive, and somehow, your group interests clash with another group’s interests, so there’s a true conflict that might draw some lines and settle new ways to do stuff up, caring always on survival and avoiding the infected over anything else. If you decided to kill everyone on sight instead, you might be an easy target for zombies and mostly you’ll get socially banned from everyone else, lol.
This is more or less what my idea of public relationships could be balanced in 4.x, compared to current 3.x messy state.