EDIT: i typed this while being rushed out the door. ill re edit it as needed if needed when i get back from dinner

Actually this can be done. first you have to turn off your client syncing with the server you can do this by typing /console synchronizeMacros 0 load up every client from all the folders you want to launch wow from.

This will keep your clients from uploading or downloading any macros you edit.

Now make the macro as you normally would on one of your clients.
Then open another client that you want the macro to be different on. Make the macro have the exact same name and make sure the macro is in the same location on the editor (the window that pops up when you type /macro)

Heres how it works and what the results should be. When you put skills on your action bars the server obviously knows which skills went where. All the macros are numbered, so say you typed /macro and made 3 macros. they are first put in alphabeticle order and placed in slots 1,2,3. If you put the 3rd macro on your action bar in say slot 2. only thing the server knows (with syncing off) is macro #3 is in slot 2 on bar one.

So as long as your macros are in the same order and named the same. the actual function of it can be different and therefore you can do what the OP requested