I like this a lot so far.
The suma she has a very high quality that will mean that she'll advance a bit faster than the 30 xp per year standard for quite some time (I'm not judging that as either good nor bad just making a note of it). I like how many seasons get put in to exposure, adventure and practice.
I would have liked to hear more about the specially bread horse that doesn't suffer from the gift. An animal can get used to the gift of one magus but not to the gift in general. Your horse should have some sort of virtue/flaw to not be affected (or a spell or an enchanted device or something) that's a story that's worth being told (of course the horse is most likely long dead by the time the character is an archmaga so perhaps it isn't so important).
I was disappointed to see the deficiency in intellego. I've done a school of the founder flambeau magus to 120 years out of apprenticeship who has a deficiency with intelligo (https://forum.atlas-games.com/t/ranulf-from-moh-now-150-years-post-apprentice/5637/1). I'd prefer to see someone take a crack at showing what is cool about intellego ignem, The character I made was dripping with muto ignem (and muto vim).
For what its worth, I think that a deficiency in intellego is about as brutal a flaw as exists in the game. Invisibility and muto imaginem spells are comparatively easy to pull off your archmaga will not typically be able to engage any magus who doesn't want to show her/him self to them. Also any other technique can in some ways be covered for by some other sorts of magi. You can destroy things without perdo, you can create things with rego craft magic or clever muto spells and so on. It is, in my opinion, more difficult to get the other techniques to do intellego than any of the other techniques.