I'm going to post this since I think you'll be able to come up with a solution rather quickly which you've proven multiple times in the past. I was using your "Remote Dorm Doors" and it hit me why can't I have a similar function with the OFB signs? As much as I love that the game devs added in the animations for walking over and flipping over the sign sometimes i really just want to close shop and get out without trying to remember where the sign was.
Such a thing already exists somewhere, friend, although I wouldn't be able to tell you off-hand where it would reside... Try checking Simlogical, please, and if that doesn't help, try searching for "remote shop sign" at MTS.