Unique Character Abilities
While Primrose and Ophelia could recruit NPCs, all of the other characters had their own unique Path Actions, like how Therion could pickpocket or how Cyrus could scrutinize characters to learn information.
Bravely Default 2 will, no doubt, feature a smaller cast of main characters, but that allows for more variation of character’s abilities.
One of the best parts of Octopath was reading the descriptions on NPCs and their daily lives, and it’d be fantastic to see that same level of detail carry over to Bravely Default 2.
It would also present unique ways to advance the story or solve puzzles. Bravely Default 2 would hugely benefit from branching design. Maybe you could pickpocket a key to make it into a dungeon, or get information out of NPCs that lets you find a hidden route.
One of the criticisms weighed against the first Bravely Default was how repetitive the latter half of the game was, and providing alternate options would be a good way to combat that worry again.
