To answer both of your questions, yes and yes(with major cost). The P99 can be converted to DAO similar to the P990 or in other words with one constant long DAO trigger pull.
You could convert it to a QA, but your going to have to pay for a new slide, new striker assy., and new locking mechanism.
So if you like the long da pull on the P99 and want this all the time, then it can be done easily. If you want a QA, you'd be better off to go buy a new one.