I have a scan program called:
OBDII Automotive Scan Tool and Virtual Dashboard
http://www.obd-2.com/
It has some nice features that would be nice in your scan tool. I had a missfire and used your scanner to pull up the P0300 code but could not tell which cylinder. I used the ODB II software and it pulled up a code with the suspect cylinder (burnt plug wire). I believe this data comes from the extended manufactures codes? Could this be incorporated into your scan tool?