I think there's more to relocating than just the city airport offering airlines a deal, and that in itself is not that easy. Citys passenger numbers have gone well in recent years but their financial performance is not so good. Their last published accounts, 2009, when FR were operating showed profits down to just over £400k. Having invested some £132.5m can't imagine the owners, who have already written the cost down, are that keen on 'deals' particularly when the airlines don't seems too keen to stay after the introductory offer ends. Some airlines may like the flexibility the comes with longer opening hours and longer runways.