I'm not sure if you COULD take Dragonwrought. Racial Emulation specifies you gain the subtypes of the mimicked race, so a Changeling mimicking a Kobold would gain the Reptilian and Dragonblood subtypes. However, he isn't a kobold. There is no Kobold subtype, so he wouldn't qualify for things as a Kobold. He could qualify for Dragonbloood or Reptilian stuff, but not Kobold.
You get subtypes as well as that...
It could be am interesting way to get into Drow or other higher LA prestige classes even if your DM rules that you need to keep the same race to continue to qualify for things. You would need to be permanently shaped into a drow in that case and an anti magic field would remove all your class features but it could be done...