Agreed - but as my Mum would say "You can have eyes bigger than your stomach"!
The airport will make much of its money from the passengers rather than the airlines. But as they will often offer "discount deals" to entice airlines to start new routes they will lose out if the routes don't survive long term - hence my comments on sustainability.
As you note at the end an airline such as Air Wales running smaller planes on profitable routes makes sense. However the demise of Air Wales and others before it may suggest that a profitable demand for some of your listed routes may not exist.