I didn't see a thread on this yet, so figured I'd check.
None of the equipment is missable anymore thanks to the Treasure Wheel. I think you can get the Zodiac summon and Ultima spell from Rendezvous battles, though I'm not 100% sure. And if you lose a party member, you can always regain them on a New Game Plus playthrough.
So there are fewer missables overall. None, if considering NG+.
That's pretty cool, Do I still have to wait till Chapter 4 to learn Ultima? I hate Luso, but I was missing him at that battle :P
You can get Ultima in the Rendezvous missions, with the appropriate units that would have the ability.