The entry on becoming a Dragonborn specifically mentions the character retains Powerful Build.Um, there was one FAQ entry which clarified that while the description in Dragonborn most often mentions humanoids, other creature types qualify to be reborn as Dragonborn as well. That means you can have Dragonborn Half Giants (which suck, due to losing Powerful Build), Dragonborn Warforged, Dragonborn Pixies, etc.
Thats about it as far as published support for Dragonborn. There are some metabreath feats for the Heart aspect, which you qualify for, but thats about it.
I hear if you go with Elan, you're invincible.
Elans are overrated, they say that because you can pay power points to reduce damage taken. The rate at which it goes might stave away massive threshold and leave you with barely any power points for powers even as a high level psion.
I suspect that he was being sarcastic, as several members of the boards (you know who you are) are very vocal in their opinion of Elan spions being broken, despite all evidence to the contrary.
Dragonborn Warforged ALSO lose their composite plating.
Losing composite plating is a bonus, not a penalty.