Correct me if I am wrong. As I understand, to establish a Council and a Conclave is a way to stabilize the North. ›››
If Philippa succeeded, yes. She would put her agents as advisers in all royal courts.
But with the Lodge gone, the Council and Conclave has no such ambitions anymore. If the mage advisers chosen have little in common, don't see eye to eye, or don't have the same leadership, they won't be able to coordinate in their influences over royal courts. That, and Radovid demands its compliance to the state.
So it's not a UN or anything (actually it kinda is in the sense of being inept). The only way it could have had some real power over states was through Philippa.