Sgt.Culpepper - I have to disagree with you re the second terminal; you only have to look at the way airports operate in the States (especially somewhere like New York) to see that competing terminals can and do work.
There's also no major difference in the way that Aer Rianta and say BAA work in terms of retailing: both own the main duty free shop, and both rent out space to third parties, forwhich they charge rent plus a concession fee (percentage of turnover).