I would Love love this. Hell just wall in east Detroit and you are good to go. I went to a concert a little while back and made reservations at a hotel before doing a little research. Well lets just say it made the Bates motel seem like a 4 star resort.
I saw on the news that entire neighborhoods are empty up there and the mayor wants to shut off utilities to that area. Detroit could make cash renting those areas to post apocalyptic movie productions and this sort of amusement park. Just keep the buildings safe enough not to hurt folks but still look run down and everything overgrown and you're set to go.
For the size they are talking, there's no way to reasonably do this. I would think from a legal reason that they'd have to have a full release of responsibility signed by any visitor for the inevitable 'accident' while being pursued by a zombie.
There are blocks and blocks with only one or two occupied household. Transients and addicts move in (squatters) until the building is condemmed and then bulldozed.
Believe it or not, they 'd probably have to raze the structures and build brand new insurance liability friendly ruined buildings. I can't see this actually coming to pass. It would be like dropping a side of beef into a piranha tank.
Sounds fun, but I want to know how the participants would be allowed to reduce the zombie population. Hordes of the undead all wearing paintball goggles would look silly, but that's what they'd need for my participation.
Sadly you'd also have the transients and addicts not to happy about folks being around, i bet gangs would also move into the area as the cops wouldn't bother going out there. Then you'd end up with more real cannibal attacks. Should just tear all those empty areas up and turn it into farm land or something useful.
Maybe instead of goggles, they could wear welding-mask flip-up masks, but more discrete. Enmasse, I'm sure it would get the illusion across. Safety first!! .... Naw, safety sucks, but not as much as a pile of law suites.