>>39803556Easy change out of the way; remake Platinum instead of DiaPer. Now that that's done, I'd say that having a proper plotline for Arceus is long overdue. I'd combine the Sinjoh ruins with the azure flute event, as well as some other end-game shenanigans that revolve more around exploration. Maybe something like the sevii islands mixed with the underwater ruins from BW2. Also, change Cyrus's motivation back to his Japanese one, and make Team Galactic have more presence (maybe even Saturn taking over for the end-game to try capturing arceus).
Also, more lore in general. That's the one thing that Sinnoh undeniably did well.