a lot of the technologie used by the garlean are from the allagan, you can see some of them robot being inspired from the allagan one. anyway, my statement stay true, the emperor, the leader of the great empire coming alone with one big ships? in a country that did push back 2 invasion? even the dumbest man will not do this. you can be sure that the emperor have a huge fleet with him, i will not be surprise if the 24 raid will make us fight the garlean into the big ship first, before send us into another place.
see how garlean ship from the V1 is close of the ufo
other point, since the V1 more of 5-7 years did pass, don't you think them technologie of airship didn't evolve? it's enough to look at the big ship of the emperor for notice the change.
finally i doubt Yoshida and it team, will have bring the leader of the most important faction of the world into the story, for be a second role! indeed the ascien are a massive threat, but the empire is far more threatening eorzea. soo far, what we did face was a legion abandonned by the empire, even nero was saying how outdated the tool the legion of gaius was still using. the empire don't have only one legion. with the struggle of power finished and a new leader nominated, you can be certain that the emperor will resume the operation to take control of eorzea, since it's the best place for make appear the primal. if he want to make sure that the primal don't appear anymore, he need to take control of this continent!
i feel that the next story arc will be the return of niddhog and the start of the new war with the empire! not the one we did face soo far, but the full strength of the empire. you can mark my word. Ascien is a threat that will go on for long, but soo far, they need to give us new enemy, with the end of the 3.0 story arc, we only have a dragon that need to reform him troops and what? nothing.
ps: one important point, Yoshida did said that the new 24 raid will not be allagan.... then... what it leave us? Garlean!