Simple suggestion. In sandbox mode, where we have the option of making zombies pathetic infantile creatures that couldn't tear their way out of a paper sack, much less into your flesh, surrounded by loot galore, you should also have no limits on traits. No limit meaning you can have all the positive traits with none of the negatives if you choose, and possibly have the ability to take traits multiple times (stacking) that way you can be a superman who can carry the world on his shoulders and be extremely resillient to infection, surrounded by strong and fast zombies that will destroy you at a moments notice.