Or, in reality, further cements the belief that magic is a force of destruction, used to oppress those who do not have access to it, because who will it be used against primarily? Commoners, and common-born soldiers. You're talking about them being bandit-killers but, come on, let's be real here.
It is a force of destruction, there is no hiding that fact.
And Commoners and Common Born soldiers that happened to be pick a bad place to be bandits, pillagers or otherwise a nuisance. It will however reinforce that this force of destruction is only unleashed upon those who are rightfully guilty of being a menace to society as a whole.
Magic already has many uses outside of the battlefield. And how is offering the ability to conjure up firestorms and black-holes to anyone with a big enough wallet supposed to make Thedas more stable?
Magic has many uses outside the battlefield, that commoners are never exposed to, but honestly that might be for the better. You know, beyond enchanting services, that should still be publicly accessible, but healing and other skillsets should still be reserved for the higher tiered citizenry, or at least until the practice becomes more common place.
How? Simple, it will be plied trade designed to target those who are engaging in practices that viewed as abominable, if you will forgive the term. I figured, the Chantry and State in question, could dictate what constitutes a legal contract within territories or not, It wouldn't be as if a random person could march to the circle and approach on matters of leveling the entirety of Nevarra city just because they happened to have a bit of gold in their pouch.
It isn't a perfect outline, but does offer a service sorely needed in Thedas, from a group that is otherwise just sitting in towers across the landing, whining about not wanting to be in towers. Of course, the money used from this commissions will also go to expanding and outfitting the Templar Order, what with the focus on the war magic needed for this, you will surely need more Templars and better quality ones that.
It isn't as if this is going to be transformed into a policing agency or anything of the sort, its just a thought regarding the usage of mages in Thedas to the actual benefit of the public.