In typical fashion... I have to point out there are a few problems with this. (Yes, even if it's just a dream.)
-What happens during the Hildibrand story is... widely acknowledged to not adhere to the rules of reality. Cyr explicitly questions whether or not he's left the realm of logic during one of his 3.x quests.
-Varis zos Galvus' opinion on van Baelsar is unknown. Given any stragglers of the XIVth were marked for death and as far as we know Varis has not rescinded this order, I do not think he has a favorable opinion of them.
-van Baelsar explicitly states he desires to take over Eorzea because he considers its leadership impotent, and that it is right of him to do so since we cannot stop him.
-As with the rest of the XIVth, Nero is a renegade from a rogue Legion marked for death in Garlemald. That's why he doesn't return to the Empire despite expressing disdain for Eorzeans. This bit is just my personal opinion, but I do not think he was particularly loyal to Gaius either - he complained about being a distant second choice as van Baelsar's chief engineer behind Cid, despite the latter being an expatriate who deserted his homeland. (I wouldn't be particularly loyal to a boss whose attitude toward me was "You're not the best, but... ehh, I guess you'll make do. I wish I had the other guy though.")
I wouldn't mind a Garlemald expansion, but our reason for going there would have to be very well thought-out and explained. (Since it's the only bit of charted land left besides Thavnair, we're pretty much bound for it next.) Garlemald itself could easily be classified as Lawful Evil, so there'd need to be a dramatic shift or change in their social and political systems for us to head there under any terms but hostile. I refrain from dealing in "What if?"s and possibilities as well, since there are simply too many to account for them all.
I question how we're going to Garlemald and whether or not it's under hostile terms. We'll find out in, what...? A year and a half? Two years? We think, maybe? Until then, I'll continue to weeb out with my katana that glows when I draw it (and/or they make DRK fun to play again).
If any extant character were to serve as our bridge to Garlemald, I would have preferred van Hydrus over van Baelsar. He seemed to be catching on to the idea that, for all their power and grandeur, the Allagans fell for a reason - so why emulate them? Unfortunately he died, and I accept that.