In the current context, the file is actually a relational database...a CSV really isn't possible without a major DB change. I don't see us changing that in existing DSP very quickly, although we would still like to. In the new DSP for the new CPU, it is a single file as you mentioned. We do expand into multiple temp files, and the temp format could in fact be CSV, with very little effort...but there isn't a real benefit for it to be.
Sadly, the new import/export will be a bit more restrictive then in the past, due to the need to maintain a memory map with the program and docs. Not sure what that will translate into from your perspective, but we will try an be as flexible as possible knowing that folks like to use Excel and such.