Yeah, let's homogenize all the different nations and cultures of Thedas into one Orlesian knock off. It'll be so much more boring that way!!
/sarcasm
For one you don't need to dis everyone's opinion and two and unified thedas is only a good thing. and culture melding would bring both ferelden and orlesian things together. you see a big example of this in New Orleans. which has heavy french and spanish influence and has create a new culture out of that wish dishes and music influenced heavenly by both.
Culture changes. Ash warrior being Vanguard for Chevaliers. now that's a scary sight.
Orlesian university accepting ferelden scholars to bring knowledge in and bring knowledge back to ferelden to then use to better more peoples life. doesn't sound like that bad of a dream. and again it is just a dream. i could also dream ferelden wasn't so isolationist and would actually attempt to help thedas. but that doesn't mean it will happen.
What could possibly go wrong? I'm sure create a new empire in Thedas that represent humanity and absorbing other nations with diverse culture will be that simple. They all will understand that the common threat like Qunari or Tevinter Imperium threaten them all, and thus they will work together...oh wait.
and do remember i said IT WAS A DREAM and it was also joke i was making to a friend. do you think i believe its possible? of course not. if it did happen would it help thedas? yes. but i dont think its possible one bit. before trying to make a counter argument know what i speak of and the mood i say it in.