Originally Posted by X-Maniac
If we are to have continuity and a shared universe, then we need to know why characters appear or disappear. Angel Salvadore and Riptide could be captured on a mission, even if that takes place off screen before the film begins. Azazel is more tricky because as a teleporter he would escape human attempts to capture or imprison him.
That's not entirely true. I would've liked Nightcrawler in X3 as well, but he did have a complete arc in X2 and it was never said that he joined the X-Men. No explanation was really needed in X3 because it could be assumed that he moved on.
However, Angel and co. were shown to be part of the Brotherhood at the end of FC. I would love for Angel and Riptide to be removed from the sequel to make room for more interesting/relevant characters (Azazel is cool visually and has a possible connection to Mystique and Nightcrawler), but yeah, it would need an explanation.