Best of both worlds a.k.a. all the benefits, no political costs?

Thought for the day following a couple of conversations over the past few days. A number of potential benefits of all-island co-operation have been claimed e.g. mobile phone costs, electricity market. ASSUME all the claimed benefits are true and the practical difficulties can be overcome e.g. creating a common electricity market from a public monopoly and a private regulated industry. These benefits could come about as a result of Irish unification instead they are being offered through co-operation. The nationalist assumption seems to be that the value of these individual improvements will make people see the benefits of doing everything on an all-island basis. However, to shift the paradigm, is Irish nationalism giving away the benefits of unity? Why would a majority vote for unity if they already get the gains with no pain? Also is the creation of an all-Ireland market not a stepping stone to a British Isles market?