The thing to remember is though, SE themselves do not seem to know what to do with Hildibrand anymore - he was originally created as part of the Seventh Umbral Era storyline in the original version of FFXIV (version 1.0) as a bit of light-hearted comic relief (initially connected to the quest to unlock the Inn) in a main scenario and setting that was getting increasingly dark and depressing. And he was brought back in ARR to kind of give some closure to his story, but carefully sent off in a such a way that he could be brought back at a later stage.
However, SE themselves did not seem to have any plans to do that - in HW the much maligned scholisate quests in Ishgard were meant to be a replacement for them (they after all feature Inspector Briardien as a major npc), but their more serious tone (as well as being a pretty obvious reference to
Harry Potter) probably did not win as many fans as Hildibrand did.
So they belatedly brought him back.... but without a specific direction from him. He's just mindless slapstick comedy, nothing more (not a bad thing at all of course). And that continued in SB, and will probably be the case here in ShB as well.
It's almost as if SE doesn't
want to bring him back, but because players keep requesting him to, they oblidge.
As for how he could show up on the First, given the revelation during ShB's story that
everyone on the First are 'soul fragments' of people on the Source (it's to explain why there are... certain similar npcs with similar appearences and names on the First to certain npcs on the Source),
maybe the player bumps into someone
like Hildibrand, but is also... 'different'.... But I'll leave that theory alone for now.
