Archer Belby is the reason Rhych literally exists, so I suspect there will be some threads between them. I was thinking Rhych would detest Fleur Rey just because she's upper class. And he might want to be friends with Thomas Montgomery, if for any reason but to free his toad, Terry, from being "his loyal test subject."
OMG, I love musicals and your list has quite a few awesome ones. We must talk about which songs we must do with our characters. Archer has to be "Schadenfreude" and maybe "Magic to Do" with Thomas. What? No "Epiphany" from Sweeney Todd?