If there's one thing Zelda games usually get right, it's creating interesting NPCs, and Link's Awakening is no exception there. Whether it's the doting Madame MeowMeow or the absentminded Tarin, Koholint Island's quirky characters stick with you even though they don't say a whole lot. That said, they could certainly be expanded upon in the Switch version.
For example, Marin feels fairly generic — she sings a song, talks about the song she sings, and likes chickens. It seems only right that she should get a bit more development in Link's Awakening for Switch, if only to explain how she came by this obviously powerful and sacred song of hers.
All of the other bizarre and lovable characters should get some additional attention too. Breath of the Wild's NPCs each had their own stories and, while they may have had less interesting personalities overall, they were more developed due to their increased interactions with Link. Giving the same treatment to characters like Papahl and Crazy Tracy would make Link's Awakening a lot deeper and more enjoyable.
It would also serve to make Koholint Island feel more like a real place — a place that Link wouldn't want to leave. For new players approaching the game without the rosy hue of nostalgia, it might be difficult to get invested without more elaborated NPCs.
And while we're at it, let's hope we get some bigger text boxes too. That would make sure that the moments created by the NPCs get all the emphasis that they need.