Not completely sold on Runemothers and Runedaughters given the patriarchal society Fyreslayers are supposed to be, but more women in general could be cool (what about that mining guild?).
Mini-salamander cavalry and a tweaked Runemaster would really enhance the faction, IMO, but I love love love the idea of exploding berserker dwarves and rune golems (especially the golems), and this is the first time I've heard either of those suggested. Brilliant idea!