Sounds like a good wish. See Writing a good feature request. but what I would recommend now is copy and pasting multipe instruments of the same granular engine, tweaking the position of the grain, size, envelopes etc and playing these multiple instruements back in a seperate track and rendering and loading that into an instrument.
It is kind of like having endless granular options and you can get some really interesting sounds this way you wouldn’t get by just adding a few more grains.