I'll start with an example of what I do with my LAN so that would give a better idea about the reason why I ask the following feature.
I Have 3 computers connected on a LAN through a switch and one of the computers is connected 24/7 and is connected to the internet.
When I want to d/l something which will take a long time to d/l I log remotely to the computer which is on 24/7 and I start the d/l through it.
The day after when I turn my computer again I log remotely to that computer and use the file transfer to d/l all which was downloaded during the night so that brings me to the feature I'm about to suggest.
To have the ability to make certain dirs with 'Share and sync this directory with computer x, y, z on the network' , what this feature should do is this :
Lets say you choose the dir C:\some-shared-directory\ and mark it with the feature I've suggested above so then whenever one of the computer x, y, z is connected to the LAN an automatic file transfer will begin and copy the files in C:\some-shared-directory\ to the other computer.