You still seem to be a bit confused with the whole thing. I am not talking about doing short haul point to point flying, I am talking about connecting long haul traffic, where in most cases businesses will pay for business/first, especially if the employee or executive is expected to work after deplaning. If businesses can't as you say justify the cost then why do the airlines still offer it? Simple really. A full business class on a 747/777/A340/A330 pays for the rest of a the flight, even with an empty economy an airlines would still turn a profit with a full business class. Some routes exist only because of this kind of business traffic, particularly in Africa/Asia/ME.
Now if a business through their travel dept. pays for a full J/C fare from Singapore to Dublin they would surely expect a J/C level of service all the way to their destination. Right now that is not possible and it doesn't send out a good image of Ireland.
The government with our taxpayers money owns nearly 30% of Aer Lingus, technically that would make EI the national airline. Ryanair would be the unofficial national airline, but I've yet to see a budget point-to-point airline that doesn't offer flexible ticketinng, interlining and codesharing ever be declared a national airline.