If the routes don't stack up or appeal to an airline as profitable in isolation why would it work as a round robin and who would operate it?
I was thinking that as Ryanair operate from Dublin to both airports, a linking flight in between might be feasable and utilise existing slots/assets.
Bit more on the Excelsis thing in D&S Times, looking at a £220 return fare to include catering and chauffeur driven car from home to airport.