I do remember that dialogue, actually...and I don't make a habit of reading Garland Tools so I likely found it in game.

I don't think it's a deleted scene. The NPCs are scattered around Ishgard, so you have to roam around looking for them. Not sure about Aymeric, though. It might have been when we were saying our goodbyes before heading to Azys Lla.

There were actually a couple ceremonies that I remember. Ishgard joining the Alliance was not actually in the credits at the end...we had that whole Eorzean Alliance mock military battle after that (after the failed peace conference), and then at the very end in the credits, we had Ishgard properly allied with Hraesvelgr's brood. I could be remembering wrong, of course, because it's way past my bedtime... XD