Just some ideas as I am using FB a lot these days.
1) More options for distortion or more ways to distort
2) More ways to mangle sound through the fitlers (Like Massive's feedback)
3) internal limiter maybe ? With on/off switch.
I have been using this loads on Hardcore kicks, it really can produce some awesome things, I know a lot of producers use it too, so an update with more options for filter processing and sound mangling would be good. The tubeamps etc are what is most common used.