This type of 'Upload' is common to PLC's (Programmable Logic Controllers - Industrial control systems basically), however isnt done by reverse compiling the code.
The code is written to flash like normal, but the uncompiled code is also able to be uploaded to memory and saved as a file basically. Then when an upload is done, the file is basically downloaded off the processor and opened with the editor.
Most likely not possible with AVR's as the memory may be too small and most likely wouldnt support this, however could most likely be done if you attached a SD sheild (or the like) - however the IDE would need to be modified in order to get the automated upload of the uncompiled code to SD, most likely.
Something to ponder on.
I am an Automation Engineer by trade, and use PLC's everyday, and this feature is very appealing especially if your backup is lost or you 'inherit' a PLC which was programmed some time ago and you have no source code.