I like the idea (well, all of your ideas, actually) but the problem is the cost to produce it. So many zombies would make the show go practically bankrupt what with all the costs for makeup, costumes, prosthetics, the actors themselves, etc. I distinctly remember that was why there were so "few" zombies in season two. Now, of course, the show is even more popular than it was back then, so maybe money isn't as big of an issue anymore. I don't know.