In my opinion, I thought Phantasy Star III was a fairly fun game, even if it does have its flaws, there has to be atleast a single thing in the game like.
If Phantasy III was extended, what would you suggest be added to it? These would be my ideas:
Rhys' quest honestly seems long enough to me. If you suggest anything be added to it, feel free to share.
Nial's quest easily could be extended upon, and also a way to shorten it. When you get to Alair in Divisia, her instict is to fight Nial and the cyborgs. After you beat her, she apologises and goes to find Lune to try and get him to stop.
When you find Ryan in the Rebel Cave, he instead comes with the Snow gem, a removed gem from the original cave. This opens the Elysium-Aridia passage, saving backtracking through Landen. Perhaps you could get the Twins Ruby at the start of the third generation, but eitherway, this cave is exclusive to Nial and his children, like how the Aridia-Draconia passage is only for Ayn and his children.
I have some other ideas that I'll post later. Feel free to share your thoughts.