It does seems like a lot of work just to send a string and manipulate a file, but you’re on the right track. That’s how it should be done. Regarding the setup that you already had, I believe that SPP is the most adequate profile to accomplish the desired behavior. You could also take a look at FTP (file transfer protocol), among the several profiles that come in the Edison Bluetooth Guide SPP and FTP are the ones that would work best.
As you can see in the Bluetooth Guide, the Edison module supports all BlueZ profiles but just some of them have been validated, you might want to check the other profiles available in the BlueZ site as you might find some helpful information.