I think that's possible, but in your model, the lower average distance has indeed decreased. Yeah, the total range (or maybe the convex hull of the idea space) is bigger, but it's not obvious that the range is what we should think about. If the top 100 proposals are small variations on the "most attractive" old idea, then a lot hangs on whether that idea is really good or not - which in turn suggests that the proposals are probably not providing enough diversity.