The 4 airports mentioned are always going to take passengers off CWL but with the right investment and airlines CWL can be a viable airport for the country.
First of all I think the point is that CWL should be trying to take passengers away from the other 4 and not vice versa whilst suggesting that CWL can be a viable airport for Wales is similar to suggesting that DUB can be a viable airport for Ireland.
Then why does Ireland also have international airports in SNN and ORK to name but two, never mind the regional airports, yes DUB is a viable airport for Ireland but, if it didn't have connecting flights, it can only serve a portion oif Ireland much the same as CWL that, besides Holyhead, doesn't have connecting flights and can only serve a portion of Wales.
If only Air Wales had stuck with Do228's then they might still be going, allbeit on minimal profits, providing puddle jumper services around the airports of Wales!