I'd like to see it work through stages of the hit of the infection. Like you start at a supermarket with lots of uninfected people around, and someone screams and they're being bitten/attacked. Work your way out.
I'd like to see you start with little to no weapons, work your way up. Fisticuffs to claw hammer to pistol. That kind of thing. Along with this, the number of zombies would have to increase. Only a few at the beginning of the infection, and increasing throughout.
I'd like to see items carried on-zombie incorporated more, like the batons on security cops and bile on the CEDA guys in L4D2. Down an infected cop, and get his pistol.
I think the dog idea is cool, along with the survivors.
Really though, if they come out with another one, I'll be happy.