Well, realistically Ilberd doesn't have a shred of hope rallying a bunch of rag-tag Ala Mhigans to his side and then throwing them at his homeland to reclaim it. That would require Garlemald to be portrayed in a highly incompetent manner. We also know that Ilberd is willing to go to great lengths - his brand of 'righteousness' involves murdering his own allies and scheming to harm a foreign monarch along with various other dubious decisions. So, to me, if the masked man is Ilberd then I believe it safe to assume that he has outside help and will resort to something horrible in an attempt to liberate his nation.

3.4 should provide some solid answers though. Yet any attempt to reclaim Ala Mhigo isn't going to be clean or justified - it's going to be messy. One could say it'd be a storm of blood, even. Yet with all the talk of cycles and history repeating itself Ilberd's actions could be the very thing that ends up forging peace and stable bonds between Eorzea and Garlemald's more moderate elements.