You can do your own tool if you have the play by play. All the information is in there except who lost the ball after a steal. Perhaps that's what you should ask to be added.
You also have the BBApi which can already be used to download boxscores and build most advanced stats. Ultimately for advanced stats you need both individual and team aggregations, so boxscore is fine. For example I think you could calculate AST% and BLK% or ORtg DRtg from the boxscores.
The only thing the boxscores won't give you is the type of shot, the lineups, who defended who and who assisted who. Boxscores also lack team rebounds and turnovers (i.e. 24 second violations or the famous rebounds going out of bounds)
You could get something like this very easily from the BBApi:
http://tinypic.com/r/2emieer/9You can ask anyone with some coding knowledge to help you.
I have my own pbp analyser, which works fine and I planned to use for scouting and create advanced or detailed stats. I still need to finish the analysis part, but I won't share this with others as it took me quite some time to put together and I always planned to use it to help my NT and U21 among other things.