difficult question about backing up profile saves

[mpgwhoop]

If I want to backup saves manually, I'm not sure it is possible to do anymore with the DLC characters.

I tried transferring my save to another. It gave me all level 1s and made me accept T&C again. Just to make sure, I bought the DLCs, and it still wiped my save progress.

I couldn't find my old save, so I downloaded one from here. That worked, except it had level 1 DLC characters, and I no longer have any of the DLC trainables.

So why is it that, a save with level 1 DLC characters works, but if you try a legitimate main save with the DLC characters played with, the game will wipe the progress (how does it tell?). Is there no way to transfer/backup a save with the DLC characters? Would it work if I played the DLC characters above level 1, then tried again with the main save?

I'm worried about losing all progress on my main account now, since any alteration might irrevocably reset everything back to level 1. If our saves get corrupted we're basically screwed?