I'm a little weird, because on one hand I could see Blade and Fang as siblings, because of Blades similar look to Kakashi, but then you have Azure (a shade of blue) Fang so you could in fact call her Blue Fang... hmm where have I heard something like that before... oh yeah Kakashi's dad was The White Fang of Konoha. If I * to this thinking I'm definitely in the camp of BladeXDancer and FangXFist (don't ask me why, but I think they work).

Now to Haku... I mean Scarlet Blaze... I personally see him as the typical Haku trap character with the feminine look, but being a dude. However, what if Scarlet is actual a twin? Non-Identital twin with a Female sibling? Scarlet even though it is supposed to be used in the sense of the car red for fire, but is also a woman's name. In this setting I definitely see the pairings more like... BladeXFang (If you don't take in a count of the Kakashi tie in/sibling theory), (Fem)BlazeXFist, (Male)BlazeXDancer...

I don't know I over think things at times