The main condition is the government's consent. Any order or group when within a nation are prone to the will of the government of said nation. If the order does something the government doesn't like, they are branded as criminals. Look at what happened at Warden's Peak. Or any of the many orders on Earth like the Knights Templar. The government has every right to interfere since the groups are in their yard. They only don't because they made conditions with said orders, pretty much "If you don't do anything we don't like, you can stay here". It will not be easy to convince the nations that your order is better for too many reasons to list. But the list boils down to "You need them, they don't need you."
Okay, you want one: Dragon Age Lore. The Book of Thedas, which is pretty much the Word of God until further notice.
Again, the governments at best tolerate the Grey Wardens. And like everything else, the Grey Wardens follow conditions, granted unofficial ones. They need the goodwill of the governments to operate. Killing citizens of those nations doesn't do that. To use your own words, you're naive if you think differently.
LoL wardens in keep openly tried mess with politics overthrowing king thing they shouldn't do and why they were kicked from ferelden as i said i plan grey warden like organization they are accepted as long they don't mess with politics and focus on darkspawn same for templars just instead darkspawn foucus on mages..
As i said goverment can't interfere in matter of templars or grey wardens (read recruitment of grey wardens or other wardens matter and mages in templar case) so both grey warden can do whatever they want as long they don't mess with country politics...
So no neither king or noble can decide what to do with mages that is up to templars and that is ther jurisdiction and country don't have any to say here examples alistair , amells and few other nobles.
As yes grey wardens are needed as well anti-mages...
LoL you are keep saying me theoretical function of seekers not practical it is only conception of seekers not how they rly work...
Eee again nope grey wardens everywhere are heroes (outside ferelden) not only tolerated... everyone know they are necessity to deal with darkspawn... also they as i said are seen as heroes As i said 1000 times because you ignore that GREY WARDEN DEAL WITH DARKSPAWN THAT IS THEIR FOCUS AS TEMPLAR DEAL WITH MAGES THAT IS THEIR FOCUS NEITHER CAN JUST KILL CITIZENS BUT BOTH CAN KILL GROUPS THAT THEY FOCUS SO GREY WARDEN CAN KILL/HAVE TO KILL DARKSPAWN AND TEMPLARS CAN/OFTEN HAVE TO KILL MAGE AS MAGES ARE UNDER TEMPLARS CONTROL NOT COUNTRY COUNTRY CITIZENS ARE UNDER COUNTRY CONTROL NOT TEMPLARS BUT MAGES AREN'T IN THAT GROUP AND THEY ARE UNDER TEMPLAR CONTROL...
Some of the nobles did support the mages though. :/
The templars had most of the political power in Kirkwall, that isn't the case in the rest of Thedas. The nobles in Kirkwall have no forces to stand up to the templars with and once again this is a completely different situation to the one you are proposing.
Having a mage in the family is seen as a dishonor but it's not always felt as one, we have many examples that prove this and they are sent to the circle because that is meant to be the best place for them.
Annulment is not something the Templars can just decide to do and neither is tranquility. Kirkwall is not a good example of this because Meredith had all the political power after the viscount and Elthina died and even when they were alive, neither did much to resist her.
Some yep but some can't do crap if they tried they would ****** off rest of the nobles and folks pretty much like amell who had to spend fortune to hide that in his family were mages still he failed neither they could do anything about templars taking away their children.
If your hawke is mage and you will go to party in MoTA you can hear what sane woman would want marry mage from orlesian noblewoman... mages are danger peoples want to be safe as well mages are seen by majority as outcasts...
We have few examples of that most stories from mages are that parent hated them and throw them out...
RoA is decided by chantry and doesn't matter chantry isn't goverment organization in fact templars are part of that organization...