gaelgeoir - actually no contradiction. The cities I listed have 5-10 times more catchment than ORK or SNN. Those cities could support 767/777 when ORK/SNN would struggle to fill 757s and A319s without the stick of government policy forcing operators to find ways of forcing people to use them. LHR is at peak slot capacity and the services I referred to are currently operated by 744s.
840 - you're right. Redirecting international traffic to DUB would have to involve improving rail service between Dublin Airport and the rest of the country in order to make the environmental argument stick. Unfortunately the fact that DART will not serve DUB instead of Metro will enforce a two-change journey on people south of Greater Dublin. Personally I think both Metro and DART (from near Howth) will be needed to manage DUB passenger demand properly.