I hope this helps clear some things up for you.
The area from Fear Factor to MIB can not be used due to crowd levels. It can become a real hazard to have scareactors in that area and the paths are just not wide enough to handle a scarezone. That small section of park has to handle the entrances of 3 houses, the exits of 3 houses, the entrance and exit of MIB, the crowds trying to get in and out of the FF Stage, and a beer cart (which could be moved I guess). There used to be a time when roaming hordes would be located there but it just became to unsafe as the event grew. Just look at San Fran, the past 2 years there where many nights when they had to pull the scareactors off the streets or tell them to stand to the sides because it just became to hazardous to be scaring people.
As for the other areas:
KidZone- This one could be used if they wanted but it's also a bit of a dead end in the park.
Springfield- Can be "used" for HHN but can't have set pieces. Which is why it's usually just a hoard there and never officially listed on the map.
London- Can't be used at all during the event. JK wants nothing to do with HHN. Heck, they even got in trouble just for having red lights on the facades. (This one is a real shame because they could do some awesome zones there)
On topic though, I think using South Street for a zone is a great idea. You've got a street not widely traveled, larger sidewalks, and access to Sting Alley.