Sorting crags by number of routes in selected grade

When filtering crags by a specific grade, I would like the list view to be sorted based on the number of routes that match that grade. Right now, filtering by grades like 5–7b feels a bit pointless, since these grades are very common. For example, if I filter for 6a in Stockholm, almost every crag shows up. However, if the crags were then sorted by the number of 6a routes, it would be much more valuable and help prioritize where to go.