So, the 3dF used in Atori's file is a great way to get the FUDGE/FATE feel of bell-curve and range of results. But - confession time - I hate FUDGE's spread of results. The 3dF has a rnage of 7 categories of results (!), which is way too high in my opinion (even if +3 or -3 are quite rare). Ars Magica's range of about 3 categories is much better.
The FUDGE dice also makes it quite hard to produce botches at a reasonable rate.
So a more direct port of Ars Magica would be something like...
Introducing the ArM Dice!
Take a d10, paint-over sides sides 10-9 as "+1", sides 8-3 as "0", side 2 as "-1", and side 1 as a bright, shining red "-1".
Now, make rolls using 1 ArM dice, instead of 3dF. You usually get Ars Magica's normal spread of three categories (-1, 0, or +1), but sometimes you get a "red" -1. On a simple roll, count it as -1. But on a stress roll - you also need to check for a botch! Just pick up some more ArM dice, and hope you don't get any more reds. (Or some regular d10s if you don't feel like painting over lots of d10s.)
This gives the usual spread of 3 result categories, with the FUDGE non-equal probability, and preserves the chances for botch as in standard Ars Magica.
Love the idea of a Fate conversion. You've done an amazing job @Atori . A few questions and suggestions
(1) Should there be stunts or aspects connected with your house? If stunts, here are some:
Bonisagus. Magic theory/parma +1
Tremere. +2 MT/parma in duels
Guernicus. +1 influence & investigate w/ hermetic mages
Mercere. +1 Muto
Bjornaer. Change to heartbeast
Criamon. Use Lore for another roll
Merinita. No penalty for faerie aura
Verditius. 1/2 difficulty for magic item crafting
Ex Misc. Varies
Flambeau. IG or PE +1
Jerbiton. +1 to art or academic roll
Tytalus. Refresh +1
(2) Simplified Vis economy. Use resources rolls instead of bookkeeping. Mercurians halve the level of ritual before rolling against Resource. Verditius halve the level of item before rolling.
Covenant can give a +1 bonus to resource rolls that take place on premises. Each vis resource roll by a character increases the ease factor of further resource rolls by that character in the same year by +1.
Characters focused on rituals or crafting need to sink levels into Resource skill. Other characters can try to give advantages to the caster of a ritual as per Fate rules.
(3) Can nationality, House, and concept (listed as aspects on the character sheet) be invoked? If so, should the character narrow their definition ? Maybe Bonisagus becomes ridiculously well read or eye for strange magic
I was thinking covenants are communistic monasteries, so characters dont have resource skill, they use covenant's resource. If they take Wealthy boon, it's propably superb.
I dont have any idea how to implement Vis Resouce, but it would be interesting to do covenant FATE style.
Build a tree for Art summae, Spell books, vis resouce, vis stocks and specialists.
Hooks and boons work pretty well as in AM 5e