Wow, if that's the case then he's a great White Sonia sub, and she just got way more legit as a farmable lead. What other farmable dragon subs are rainbow-friendly?
She still needs the green slot filled, but I don't think she cares about Draggie that much because she already has an enhance herself. Maybe Zhao Yun? His active isn't great, but it's not nothing. I guess you could also use any fruit dragon for green too, since although their active breaks Sonia's leader skill it would still be handy for stalling, and all of the awakenings would be useful.
WSonia/Volsungr/Volsungr/Defoud/Zhao Yun or Lemon Dragon/WSonia
Kind of low-utility, but for a 100% farmable team it seems like it packs a lot of punch.