If I understand your proposal properly, you're having trouble dragging files into the Finder because your app is sandboxed and you the don't have the permission to write files to disk. I just put together a small example application that writes a file to any destination from a drag from inside a sandboxed application.
I posted a video of it at [login to view URL] In the video, you can see me turn on sandboxing, run the app, drag a file to the desktop, then open the file from the desktop in TextEdit.
If this is your problem, I could probably have it fixed for you within a day.
Please contact me with any questions.