I would also expect a glissando (perhaps using pitch bend) to be easier to programme than the trills but Daniel and his brilliant colleagues no doubt have their own views on that one!
Another thing I’d like to see in this area it an improvement in the rendering of two note tremolos where samples are usually lacking. I must say I agree with @Alberto_Maria and others who say that ornaments are a virtually impossible job because of the huge varieties in interpretative practice.