I don't see anything inherently wrong with wanting to read back the current output state of an analog output. The wiring API doesn't support it so it would be a non-standard feature. It would be simple to either modify the implementation of analogWrite() or create your own wrapper function around analogWrite() to store the data, and add a new API to retrieve it. The wiring API is far from perfect and the analog input and output functions could IMO be improved (give them less misleading names, for a start, and then sort out the daft pin numbering scheme) and I would regard this as an enhancement - just not one that many people are going to be clamoring for.