players are from all over the world, and are on at different times, making it really difficult to swap upgrade material with people in your neighbourhood. we keep missing each other. It would be nice to have a box on your farm that neighbours can drop items (especially upgrade materials) in when you are offline.

If you really want to get fancy, you can put up tape for example, and then select what you want to swap it for, and visitors then have to add that item, before the tape unlocks.