As far as the game's aesthetics go, that would be my biggest hope.
Space is beautiful, so I hope the devs provide some opportunities to experience that vicariously through the game's space explorer. They were sort of limited on what they could do with the old engine and old hardware, but those should no longer be issues with the Next Gen consoles and Frostbite. Even DA:I, which was still tethered to old hardware, looked great outside of the hair options in the CC.
On that note it would be cool if the ship's windows had a stunning planetary view, similar to this:

It might not be possible for every uncharted world the ship will visit, but would be cool at least. if they could pull it off for main story worlds
I 100% agree with this.
Most of what I would like for immersion would be if they accurately modeled what alien environments would look like from the surface. For example, the appearance of photosynthetic pigments can be predicted (thanks to natural selection) by the spectral output of their star. Plants on a world encircling a red dwarf would most likely be black, for example. Little things like that, and environmental effects would massively improve the immersion for me.
Another thing that has nothing to do with the game engine is the creation of accurate solar systems. In the original trilogy, they tried to do this by putting data like temperature, orbital period, gravity etc. They even accurately paid attention to tidal locking. This helped with my immersion, at least - I don't know about anyone else.
I've said this before, but it would be very accurate to create interesting solar systems in the physics simulator Universe Sandbox. You can do it within minutes. If they created solar systems that were scientifically plausible, alien environments that were hypothetically plausible, and visual effects that were stunning - the game would take sci-fi to a whole new level.
Sadly, none of that will happen, lol.