As far as I can tell it’s not possible for a Vaylen to gain the Iron Trained trait except with unused trait points, which it will be highly unlikely to have enough for. It seems rather odd to me that it isn’t available in the Commander lifepath, it seems an obvious thing that such Usurpers should need.
This is for a FoN I’m burning up for my game, and being unable to get her Iron will reduce the concept somewhat 
It’s a game balance thing. Vaylen can’t start with it, but they can gain it in play. Also, check out the Vaylen Infestation rule on page 198.
-L
That rule seems to bring up even more confusion, since it says that traits bought during Usurpation cost their normal cost, and those bought during Invasion cost 1 point … yet there is (as far as I can tell) no way of earning trait points in play. Is one allowed/supposed to save trait points from character burning for this purpose?
Pip, methinks you’ve forgotten that a group can decide to start playing in a phase other than Infiltration.
If you start your game in Infil then you’ve got plenty of time to acquire iron. While it’s not possible for a character to get die and call-on traits during a game, nothing should stop you and your character from scheming and, as a result, hulling an iron-trained character and use him as your battle avatar.
If you start your game in Usurpation or Invasion phase it’s more likely that you’ll need an iron so your character can begin possesing such tech and appropriate trait.
Just to be clear: all characters can be voted into any trait at the end of a phase. And Vaylen characters may pick up additional traits of any type when they hull another character.
-L
Also, I don’t have my book in front of me, but if I recall the rules for body transfer, a Vaylen who took the Iron Trained trait with him as a worm into another body with Corvus and Crucis could use Iron in that body as well.
Yes.