You are right about making it challenging but how do you expect that to be implemented...If its like adjustment made in the length differing the input given then it would become like a bug in the eyes of the player...
what we have now is just a region of needle stopping were it says perfect make it a lot tougher to get that i would even tie to the bowler's confidence and rhythm a lot.
Also make 'Good timing' more varied and open that window a bit so that more lengths are covered, Right now the fact that 'good window' is small is what makes it easier to land on the spot a lot make it more varied and less on the spot, I would ideally include the 'early regions' to the good length too, More of the whole range of dial [atleast half of it] can be used for more regions of the pitch instead of using them for marking bad deliveries and no balls.
Also i would make certain things more attrib based or skill based, like yorkers and short ones unless the bowler isn't built for that it doesn't mater if the user stops the needle at say short and good, it shouldn't be a vicious bouncer of an Johnson it should just be what is short and good of that bowler.
even better would be a different hud system that is more on the bowler than on the side of the screen. with the essence of what i have said above to make it challenging.