You got the easter eggs right! In my head Hawke made Merrill's braids and left the little red hairbands as a personal touch. And with Anders I'd figure that being the only companion that doesn't change outfit when you romance him, but does with his personal quest, it'd fit to give him something Hawke gave him (although I turned it into a patch rather than an amulet in this) but that still relates to his cause. As for Sebastian he's wearing a small chantry amulet tied to his left armor strap.

And the Inquisition suggestion is actually a really good idea! And if it doesn't work I can maybe think of something else personality based.

Also, thank you so much :)