Bear with me here. This is just a whimsical idea.
I have been on this retro kick lately. I will spare you the jargon. Suffice to say I am playing an old version of D&D that includes material written by John Nephew.
I have taken an interest in "clones" and this vibrant creative writing community. Different takes on the idea, cloning different mechanics, but all based on the older version of that game. Now remember, Ars Magica has its origin as an optional magic system for that game. Or something like that. Said author went on to rewrite that other game. I have nothing against it, but this stuff is inspired by several versions previous.
Which leads me to Dungeon Crawl Classics, a clone that uses a die roll for magic and interesting arcane dangers. There is also this thing the call the 0 level funnel, in which you create a few shucks, send them to their doom, and the one that survives becomes your character.
Bear with me. This is a screwy idea fusing concepts of Ars Magica to two or three retro games.
You start the saga with one Magus of the Order of Hermes (9th level magic user), one companion (9th level anything else), and 4 Grogs (o level nobodys, one may become an apprentice or companion if they live long enough).
Go ahead. Tear the idea to shreds. I enjoyed the thought and the process of writing it down for others to read.
Your idea does two things:
It fills my heart with Baldur's Gate nostalgia. And it makes me glad that we have advanced beyond those Level 1 role-playing games.
I have not progressed. I have regressed and I love it.LoL
I discovered it was never about the game, it is always about the people at the table.I am not a one game guy. There is nothing to outgrow, and tese games are pretty much all the same as long as the group is having fun. Rules are important though, as they give everyone common ground.
And there is a nostalgia factor for the old red and blue B/X. I am an old grognard, and Baldur's Gate is after my time. I left off with that game sometime in the mid 90's when ArM4 came out. Mid 2nd edition. The Mystara Monstrous Compendium just came out. That is one of several John Nephew links to the setting and version I am playing. As you know, John Nephew owns Atlas, which owns Ars Magica. He also wrote PC1 "Tall Tales of the Wee Folk", a couple of modules in the Empire of Thyatis, and I am not sure what else.
It's a fine idea.
For more variation, you might want to consider that a Cleric (or Elf, if the OSR you are using has the Elf class with near-full spellcasting progression) makes for a fine magus. Different Houses and Arts! Or, since I know who I'm talking to, different Flambeau Schools!
Yes, I am very much that OSR. Elves are a class and Clerics can become Druids at level 9. John Nephew wrote a book that lets you create a Pixie as a character class (I have one in my game).
I am also getting into clones of OSR. Things like Labyrinth Lord, BFRPG, and Dungeon Crawl Classics. It is that latter clone that made me think of using Ars Magica as a setting. They replace Vancian Casting (memorizing spells) with a die roll. High rolls mean more effective results, low rolls fail, and terrible rolls cause "warping".
I remember reading on 1d4chan once about a ars magica inspired magic system that used forms and techniques. I think it was called five by ten magic.