You know, an english teacher of mine presented me with a theory a while back. He told me he believed that zombies where the manifestation of our fear of drug abuse.
Back when zombies were created, many had irrational fears that their towns youths would be corrupted by marijuana and become stupid, mindless... "zombies". So the premise of the zombie, is that if you don't contain the problem, it will spread to every town in America and cause our entire society to collapse. And so I present to you, "So the premise of the [drug addiction], is that if you don't contain the problem, it will spread to every town in America and cause our entire society to collapse."
So today, we've become much less afraid of Marijuana. Now our zombies represent herion/cocain addicts that have been known to do some crazy things while under the influence of the said drugs. (ex. Tales of police shooting a man hopped up on herion who, despite being shot numerous times, continues to run at them until ultimately brought down.)Suddenly, it would make sense why zombies have gone from slow moving and stupid to driven and fast. Of course theres more ways to connect this, like talking about how you have to shoot them in the head or why, in some cases, only some are infected and not other, but I'm merely presenting this theory to you, not writing a research paper. Feel free to expand on this as much as you want.
I think they need to explore a time setting not often explored in video games: The begining of the outbreak. Take a sandbox game, much like the size of Dead Risin, and fill it with NPCs who do their own scrip, much like normal people would. Somewhere at random in the in game world the zombie infection would begin, starting with one person. Maybe he's in his house with his wife and kids and infects them in their home, and maybe the mailman comes and gets infected and it goes from there. Or maybe a woman NPC in a shopping mall trying on clothes infects the employee helping her, who infects the mall security guard and it goes on from there.
Then you would keep doing whatever you were doing before untill the infection reached you, and you saw some lady getting pulled out of her car and eaten. Being open world they could do a lot of things with this. You could go the Dead Rising approach and go to town, and just go to town on the zombies, or you can try to escape the infection, or maybe you just sit on your roof with some beer and a handgun and take the Romero approach and shoot some neighbors you never really liked. Of course, I'm not a game designer so I don't exactly know how advanced they'd be able to make these NPCs, but its just a thought.
This post is getting way too long so to wrap it up...
TL;DR
I think zombies represent drug addicts so I don't really mind them being all fast and everything... Hey it'd be cool for a game to take place at the begining of the infection, wouldn't it?