Ship all those that voted "Yes" in the referendum to Northern Ireland and ship all the Unionists from Northern Ireland to Scotland.
Declare the island of Ireland a new independent country: "The United Celtic Kingdom". It can stay in the EU, because it is essentially an enlargement of an existing EU State. (Just as Germany did not need to reapply when reunified). Sensibly it would use the Euro as most of the island already does and not worry about any issues with the Pound.
The Unionists moving to Scotland can reunite themselves with their Ulster Scottish roots on mainland Britain. An in out EU referendum to be held in a couple of years.