For "The Dead," how could it be argued that Gabriel's wife personifies Ireland, and Michael personifies men who loved and died for Ireland?
The key to your argument lies in Gretta. She clearly states in the story that she believes that Michael died for her:
"And what did he die of so young, Gretta? Consumption, was it?"
"I think he died for me," she answered.
ILets break down the details about Gretta: she is from the west of Ireland. Ireland is a country that was usurped by England. The British moved in during the 17th century and worked to eliminate the Irish culture, hoping to remove any threat from the natives by stripping their individuality. However, the west of Ireland - further removed from England and from the ports into which the England invaded the country - retained its culture much longer than other parts of the country. Gretta being from there gives her a more "Irish" identity.
In addition, Gretta is married to Gabriel, who represents the European influence. Gabriel is labelled as a "West Briton" by another party-goer, meaning that he has become English, despite his heritage. He is ridiculed for not wanting to visit his own country and for abandoning his true language. Being the "Briton", Gabriel dominates Gretta as England dominates Ireland. He over-protects, insisting on galoshes, and tries to prevent her from being with "her people."
Thus, Gretta clearly symbolizes the country, and Michael's death indicative of the death of young patriots for their country.
I have to compliment sullymonster on his/her excellent analysis of this question. I also wish to add a note of caution: don´t assume that characters can be interpreted in only one way. It is equally valid to say, whilst acknowledging the personification that you refer to, that Michael Furey represents living your life for love and for passion rather than duty. Look carefully at the passage at the end when Gabriel expresses intense regret that he does not love to the same extent as Michael and will never experience that love. Gabriel is a character who seems trapped in so many ways into different roles and duties that he is perhaps now regretting.
Another interpretation of Gabriel is that he represents Joyce and what would have become of him had he not left Ireland. Like Joyce, Gabriel has lost his mother at an early age, he writes for the Daily Express, he is a literary person and an English professor,he is less provincial than his contemporaries seeing the importance of absorbing European culture.
Clear personification comes with the harp which is the Irish symbol, little Chandler represents the typical Revival poet, Father Flynn, the spiritually ignorant priest, whose past contains some unmentionable shame, and Molly Ivors is the Irish Ireland (western).