Unity to 3ds Max backwards compatible?

Okay, so I am very familiar with the process of getting a max file into unity. Then if I make a change in max it will update in unity after I save the max file with the same name overwriting the previous file. If i have moved something in unity or changed a map, it will keep those changes in unity even after overwriting the max file. Here is the conundrum: I have a client that is wanting to use a unity build to move things around and re layout an environment maybe change out some maps. That is fine. I have that functionality done and built. However, they want it to update the max file. Like if they change a map in unity, they want it to update and change the map in the original max file. Or if they move an object, it would move in the max file as well. Reason is, they dont have unity. They are doing the design work and i am doing the unity work and providing them a build that they can play with and make changes, but they want the changes they make in my build to update their orignal file so they dont have to do it twice. Is that kind of backwards relationship remotely possible? Any thoughts are greatly appreciated. Thanks!