Oh, I always assumed Altissia was a peninsula and had a train station/track of its own, separate from the water bridge that you use to enter. Always thought it was the part on the right here (which says Exit). But a port town makes more sense.
You are partially right I think. The old map depicted Altissia as the end of a Peninsula to the country of Accordo. Before what we got, it looked like everything in Eos was actually connected.
I think that concept was when they were probably going to have more of Accordo to explore instead of just a part of Altissia, but as a connected continent. It looked like the boat would take you further inland, and perhaps, eventually just explore Niflheim the same way you would have with Lucis.
Here, most know about this:
But they changed Accordo to a series of Islands, however, Altissia is practically the only thing there, as the rest of Ravattrice (the main island) is unexplorable and no other islands are touched on. It almost seems like Altissia is the only location to begin with. I like that Accordo is a set of islands now, but I wished there was more to see and do there. While not to the same extent as Niflheim, it gives the same empty feeling for me.
That's why I do hope Chapters 9-13 are revamped in the same way 14 is being done. We are getting 4 DLC's now, and due to them actually spending time on each significantly more than the previous (as they say) and connecting each more closely to the main story, I can't see how some of the won't affect these chapters in some form.
Whether Ardyn's DLC opens up a part of Niflheim or Luna's let's you see another area of Lucis or Accordo, we have yet to see, but hopefully one of the others focuses on some of the core issues with these chapters, even if it is in a new way as they describe.
Tl;dr: I expect/hope these DLC do their best to bring the world we play in more to life, either through other characters (Luna and Ardyn) or through Noctis and bros directly in the main game. I'll welcome anything in the main game getting improved upon (like more story delivery for the earlier chapters), or a better prologue, or a Kingsglaive adaption, or a brotherhood adaption, or the opportunity to explore new areas (Northern Lucis, Galahd, Greater Accordo/Ravettrice, Niflheim, Tenbrae, or Gralea). ALL of it is welcome and ANY of it would improve the game. I just hope we get to see even one or two of those things. So far they've addressed what I could've wanted for insomnia (a better late game dungeon), I have some faith that a little more will happen.