Basically, the Diana system makes some skill use very easy. I think I want to add a mechanism so that the first time around easy things are easy, but if you keep on using the same shtick again and again there are penalties. Eg. Clarkson has "Drive really fast" 6, the first time he uses it he just has to roll one success, The second time and subsequent times he uses it he needs at least two successes. But if he had a second relevant skill such as "soup up vehicles" he could use that again without penalty.
I think it may be too complicated for the sort of cinematic games I have in mind - maybe the GM just needs to ask for more successes as the adventure progresses, it might be simpler.