Looks like Persona 5 might be getting the FES/Golden treatment soon.

[Lord Golbez]

There's already a reporter in the original Confidants, so I doubt they'd go that redundant. They might do someone like Marie, but again with the number of velvet room confidants that might feel too redundant.

This is kind of why I had trouble answering the question. I think some new social links would be nice but I don't see where they would work them in. A Shido social link, for example, would not be believable and would mess up the story. Maybe Ann's friend but she's really too integral to Ann's confidant arc. I think she works best just as Ann's friend. There could be a decent way to work in a completely new character but I'd have to see it. They could flesh out the part time jobs more by adding a social link in one of them. In Persona 4 there were a number of part time jobs tied to social links. In P5 there's hardly any incentive to do any job more than a couple times. Oh yeah! What about Lala from Crossroads as a confidant? That seems like it could work. I know Ohya's link already largely takes place there, but I don't think that's a huge problem. Lala's presence in those scenes isn't so much that it would preclude a social link of her own.