I checked and the earliest WoB was a bit before the release of Shadows for Silence in the Forests of Hell. So, Threnody might also not be a valid candidate. The other planets in the Drominad System are also out as they first got a mention in the Arcanum Unbounded essays. I don't think think Taldain should be counted either as White Sand graphic novels weren't out yet only the semi-canonical prose version, though an inter-Autonomy planetary scale conflict would have been interesting. Only Scadrial, Roshar, Sel and Nalthis are available as options