From linked article: “Personally, I’d love to do Advance Wars, but since it’s harder to create relationships between its characters compared to Fire Emblem, I don’t have a clear idea of what kind of setting it could have.”
One idea I thought of is that the units could STILL be nameless and lack personality. But the REAL character depth and relationships would be centred around the commanding officers. Unlike Fire Emblem, which has a myriad of individual characters, Switch Wars could have only a handful of characters--but their backstories could be deeper. Outside of battle, there could be a customisable barracks in which the commanding officers would hang out, discussing strategies, sharing past stories and whatnot--and like Fire Emblem Fates, the main character could share his/her quarters with a fellow commander whom he/she pairs off with. Behind closed doors, the avatar's mate could share dozens of personal secrets, childhood memories, and many other things. The more you bond with your partner, the more at ease they will feel around you, and thus naturally the more they'll self-disclose. And of course, the more gameplay advantages they'll offer. In a nutshell: smaller cast, more support convs. I've only played part of the first Advance Wars, so I don't know too much about the series, gameplay-wise. Though, according to the wikis, each commanding officer in Dual Strike has special abilities that affect the units in various ways. They could expand upon that.
[Shrugs] That's all I have for now. I might think of some more ideas, once I've played the rest of the games.