I have one (untested) suggestion: you could try to enable the WiFi-Server of one iPad and access it from the other one. Then you can open the files that you want to transfer in Cubasis. This could at least save the extra step over your iPad. Let me know if this worked for you.
If this does not work you will have to take the intermediate step over your computer.
I’ve tried this and I can’t seem to upload my projects back to the iPad, since I can’t upload a folder. The same problem occurs with iTunes file sharing. I can’t find a way to get my projects back into the media bay.
I hope you have a solution because otherwise there is no way to restore backed up files in case your iPad dies or gets stolen, or you need to reinstall.
That seems somewhat dramatic. In those circumstances, I would just set up a new iPad using iTunes from a backup of the old one, in which case it would be an exact clone of the old iPad including Cubasis projects and everything else. Are you saying that wouldn’t work? If not, that would be a first. I’ve upgraded iPads and iPhones in the past several times, and it was easy. I can’t see why this would be any different.