My prediction for 4.3 (Obvious Spoilers)

[Rayo]

I agree with the OP, its always seemed odd to me as to why the Garlean Bodyguard was a named NPC that can be talked to. Though it only occurred to me he might play a part when I was watching the Patch trailer that he would play an important role, and considering it shows the Pure blood Garlean/Maxima (or whatever) in a Garlean command center and shows Alphinaud in what seems to be a Garlean styled room while talking about how he's best as a Diplomat, seems to further cement the poster's theory

on a side note, I don't think the Elezen Samurai in Resistance Armor is the Elezen Bodyguard, I took a look and the two have different Eye colors, the Garlean Elezen having Dark Brown eyes, while the Elezen Sam had Blue eyes, and the only Elezen with Blue eyes I could recall is Aymeric