She's not the first though. Remember, PoFV was released August of 2005, and StB in December of the same year. Aya was once again, the fastest.
Good point, both offers good and interesting ideas for a new style of playing.
But, in the same year: Aya was 8th in popularity (2005), meanwhile Seija is 56th in 2014. If I take as reference: the year of her first appearance in a game, her first game as playable and the same year popularity ranking, Seija case is really noticeable.