Ideally, the cubbie would work like a PostOffice drop box and have a way to insert packages at will with out a code and then the owner has a key to unlock the cubbie.

Perhaps something like a old-fashioned padlock? Anyone can click it shut and then you need the key to unlock it again.

Yeah, that's the traditional package box. This is an example: http://www.pe.com/wp-content/uploads/migration/oh4/oh4e3m-b8...

The issue with that is people know if there's a package in there or not, you can't have more than one delivery service come in a single day, and you run the risk of vandals running off with your lock.

Someone is leaving dog shit on your neighbor's lawn. It's not you, you pick up after your dog, but your neighbor is convinced it's you.

Late one night, your neighbor saunters up to your drop box and empties a bag full of dog shit into it.

You seem to have great neighbors. Maybe ... talk with them?