Filtering might be a real good idea. Otherwise, you could bring the trace out somewhere on the extension connector side of the board, and 1) use a shorting block that we can unsolder; 2) put two blank pads just before the point where the AGND meets the DGND and then we can cut the trace with a knife, later soldering a short across the pads if we want to relink AGND and DGND, or best, and space and budget permitting, a jumper.
Solution #2 is certainly the cheapest, as it requires no extra parts or manufacturing steps. However, it means lots of extra effort to get AGND running, which people less versed in soldering might be scared off.
Out of curiosity, at Embedded World Nuremberg, I was told that the first production run was for 5,000 units, and that future runs would be considered if the first run sold well. Am I to understand that you guys are seeing good sales data? I sure hope so!
Cheers,
Kenn
