I will surely make Ars 6th a subscription based game as D&D Beyond.
It will be a place to automatically manage all things related to character sheets, covenants, grogs... It will be a place where the community could share objects,covenants, books, antagonist, NPCs, house rules etc. I will also made a companion mobile app so you can have your character at hand at every moment. The app will also be an "Smart" dice roller to keep calculation out of the table.
I will strongly support Roll20, making an official sheet (the actual one is really nice BTW) and selling adventures and the rules in the Roll20 Marketplace.
I will have an official YouTube saga, with the best GM and players I could afford, making all the characters, items, covenant sheets available so the audience can follow the saga and get a grip on how the game is played.
For the physical game I will create props to enhance play. Spell Books with swappable spell cards, a way to resolve Certamen with cards, an spell calculator abacus, vis cards/counter...
Also expand the IP: certamen card game. The Schism War Wargame, Covenant Management eurogame (great ideas here) and don´t be afraid to venture Ars into other RPG systems. Magic Shoe for quasitors, Savage World for Hoplites, FATE/PbTA for initiation and even D&D 5th as Cubicle7 did with The One Ring.
And I will love to read Ars Magica fiction. Timothy Ferguson wrote a very nice story that was key for some of my players to get the feeling of Ars.