One can't just make a nation of mages, unfortunately. An organization, sure.
Mages have been advisors in Thedas, and I agree it is a decent fit. You have the Court Enchanter in Orlais and the Mortalitasi in Nevarra. One needs to still be wary and have a copy of the Litany, because Nevarra almost fell to the Venatori due to blood magic (reminiscent of King Theoden in Middle Earth/Arda).
Still, they comply with the Chantry even if they strain the rules of the Circle.
The augur do have knowledge of spirits, but they are kind of subservient to them, and being possessed is unnecessary. They are at the mercy of spirits that are more readily manipulated by the thoughts of people and possibly demons who readily manipulate. However, like the seers, it is just ingrained into their culture and tradition to greatly trust spirits... which has worked out for them, but may not be adoptable by all the other cultures.
Finding ways to incorporate magic and mages into everyday society is nice, (like making holidays a little more spectacular, clinics, or whatever that won't ruin the economy or livelihoods of engineers, since tech is important,) but they live a unique life with unique obstacles that can't just be ignored. Great power, great responsibility, bla, bla, bla.
On Dorian talking about a soldier falling on a sword. 1, falling on a sword sucks for the soldier, not everyone within a mile. 2, not everyone has the discipline and will to be a good soldier, just like weak willed (or just plain stupid) mage will always be at risk of demons like a clumsy swordsman who risks impaling himself.
It would be unfortunate for one to be born with magic and a poor mind, who can easily be fooled/tricked by a demon.