Her early game dialogue is often very different but end game not really. There are instances and reminders of course, but throughout most of chapter 4 and 5 the more broken version of Altina slowly heals to be closer to her other self. Honestly I'm curious if the planned change to make recovering Altina mandatory will also mean you have to recruit her in either mode (or even just remove the more broken one). Currently there are 2 ways to not recruit her, the main way that's happening right now is just not realizing (or choosing I suppose but I doubt there are many who willingly choose to avoid a great unit) you can save her in the first place, and the second way is to never heal her emotional injuries after saving her (when you choose to do this is what determines saner/broken version) at which point she leaves during the end of chapter 2. The first is definitely going away, but I'm curious if the plan is to make not dealing with her aftercare will also not happen.
I think an optional partymember would have been neat.
I mean, my first playthrough of 'Final Fantasy 7', when I were younger, was completely without Yuffie and Vincent.
Optional stuff can be great, especially when it's something as big as this.
Also, I don't know exactly if you have to actually go into this place where Altina is being held, to move the story forward, but I remember that I nearly missed it.
The problem was, that the tile for the area is just slightly altered mountains, which makes it seem like a hidden place you need to look out for, instead of something important.
So I can see that people miss that place completely.