Rarely have to play solo, as there's usually no problem getting a game of this going in our group. But when we play, it's always a loss if anyone dies. We do character selection at random.
House rules: Rick gets +1 with a handgun. Michonne gets +1 with the katana , but everyone else gets -1; likewise with Darryl and the crossbow. Makes for an interesting little sub-game to get the right weapons to the right people.
What do you mean by +1, -1? Health?
Anyhow, just played my first game and I found it VERY brutal. Only made it to round 6.
I will try your house rules next time I play. Very similar to my own rules for Zombicide Black Plague. I start them with good weapons. Just a bit of a pain and a struggle trying to search for them. And one may not even get them unless the item deck is rigged.