Omega Soul, I can agree with you about Meloetta being the best choice. That said, and after taking a quick look on Wikipedia, since the Red Deer is the largest mammal in Ireland, perhaps Autumn Deerling or Sawsbuck would be an option or, since the Mountain Hare is also called Irish Hare, perhaps Bunnelby.
About the rule, I wan't to make all countries as equally as possible. Since in the world some countries are big players and others aren't that much important, at least here and when it comes to status as regular Pokémon, they all will be. This voting is something that can be updated with each generation so perhaps a regular Pokémon more fitting of Ireland may appear!