This would pretty much just be an atmosphere mod, changing some actors' AI and adding maybe a couple of new topics. If I were to do this, I'd make the following NPCs become members of the Council of Mages a few days after the defeat of Mannimarco:
- Raminus Polus
- Tar-Meena
- High Chancellor Ocato
- Borissean
- Gaspar Stegine
These last two would receive a promotion to Master Wizard. I'd also promote Bothiel to Master WIzard, as she would become the new Steward of the Council, replacing Raminus.
As far as Council activities, about all I would want is for them to meet once a week for a couple of hours, then return to their regular schedules. It's a small thing, but it would add atmosphere.