I haven't had kids at the door since the 80s, mainly because I live in a 4th floor walk-up. One of my friends lives in a high-rise co-op (27 floors) with the following policy:
1. Children from the building only (There is a lobby attendant to help with this).
2. Households wishing to participate are required to sign up by X date. They will receive a door decoration indicating that they are a participating household.
3. Hours for participation are set.
4. Information is distributed to parents.
No need to complicate it further.
This can't possibly apply to the OP's story--that high-rise is in no way analagous to a neighborhood.
Oh, except that the high-rise residents *also* only wish to "play the game" with kids who live in their neighborhood. So they *have* "complicated it" in exactly the way that the OP's neighbors have.
They simply have better tools (four walls and a doorman).
If someone is feeling really taken advantage of by having hordes of kids who have no connection to them, coming by, perhaps they'd have a happier Halloween night if they simply approached all their actual neighbors to say, "We're not going to give out candy, but we really want to see your kids' costumes, so have them stop by to see us before they go to the rest of the nabe." And get some full-size candy bars to pass out to them.
I was not allowed to trick-or-treat; my mom thought it was greedy, I think, or too risky in terms of misbehavior, etc. But my neighbor lady always insisted that we had to come show her our costumes (we did dress up, for school and for giving out candy), and she gave us some candy from her stash.