Anders is saying that he wants Alistair to try. That is entirely irrelevant to Alistair's own feelings in the matter which are neutral.
Mages are much more dangerous to a nation as a whole.
A smart ruler may attempt to use them but will also understand that the Circle and Templars are necessary or he will soon see his nation being controlled by mages.
Yes Anders is saying that but the idea is already in Alistair's head, its merely an encouragement. Someone who considers taking over the circle from chantry is at least slightly pro-mage. Remember its the exact thing Fiona wanted, is fiona neutral, obviously no. Only the scale of wanting it is different, the idea is the same.
You assume all mages want to control the mundane nations which is entirely false. The mages rebelled to have autonomous circle aka separation from Chantry they did not rebel to create Tevinter.
Mages are just more useful than templars in general and in every aspect. Templars are only capable of fighting mages better than mundanes and that is it. Fereldan already has Soldiers, they don't need more soldiers.
Mages can heal wounds, close possible veil tears, fight other mages if need be as good as Templars if not better, and are much better than Templars when it comes to being an asset to an army. Also their numbers are fewer yet they are more useful, less resources spent on them and more gains.
The history has shown us mages are vital. Grey Wardens absolutely need them. The fate of Thedas was decided because of them when all circles joined to help fight Qunari etc...