I'm more than well aware that Phantasy Star IV sold terribly (I think it was about 45k total sales?) so this would never have happened. I am also very well aware that the main plot ended with IV but that doesn't mean you can't simply make a new plot in a new star system - somewhat akin to what the Zenithian trilogy for the Dragon Quest games is. Just hang onto the art/music style and make improvements to the battle mechanics where necessary.
However, the Sega Saturn was a powerful 2D machine with some... mediocre 3D abilities. Pretending that we live in this fantasy world where Sega decided to throw away even more money on this franchise, what does Phantasy Star V on the Sega Saturn look and play like?
Does Sega stick with tried and true 2D one more time, or do they try and make the jump to 3D environments? Now, its not like 3D is impossible on the Saturn - the Saturn version of Grandia from what I understand is considered the definitive version. So in an strictly technical sense its not impossible to do.
I personally would love to see what ridiculous sprite manipulation could be done in 2D (see: Princess Crown for 2D insanity) and even in the late 90's Sega's programmers could probably do some really out there stuff.
I also think a transition to 3D environments would just feel weird and almost come off as derivative of the Playstation Final Fantasy games but I could swallow it if it was done well.
What changes to the classic PS formula (other than plot for obvious reasons) would you want to see?