3 compiled small updates
VIRTUES AND FLAWS
My list of V&F is something like this right now. I think I am set on them
VIRTUES (+7 pts)
+3 Mythic Blood (effect to be fully defined, but including cold resistance)
+0 Minor Focus (ice)
+0 Puissant Aquam
+1 special circumstances (cold places and weather)
+1 skinchanger (lynx)
+1 piercing gaze
+1 Animal Ken
FLAWS (-7 pts)
-3 Weak Magic Resistance (near large sources of heat, including +15 damage or above ifire spells spells)
-1 Deleterious Circumstances (very hot places and weather)
-1 Known Weakness (of course, known by the most inappropriate persons at a given time according to our SG)
-1 Incompatible Creo Herbam
-1 Magical Animal Companion (Large Winter Wolf of size +1, as per the tremere book. A friend, not a pet)
-0 Reckless (minor)
I think this defines the character quite well, in the end. Time to move to other aspects of it.
MYTHIC BLOOD:
You can see a discussion on the potential mythic blood here:
https://forum.atlas-games.com/t/mythic-blood-winter/2888/1
I think I will end up with the ability to withstand massively low temperatures with ease. Seems fitting, specially since I would like to walk around in short sleves in winter and say something like “Nice cool weather we have today, sodales!†when entering the covenant 
Yimir's Kin (ReIg30)
R: Personal, D: Sun, T: Ind
You are perfectly happy in the middle of a blizzard or wintry phenomena. Its temperature simply does not affect you. The cold there feels (at most) like a welcome chill . This spell provides a +20 soak bonus versus any kind of cold. Cold sources doing +20 damage or less simply do not affect you at all. This renders the maga effectively immune to cold damage unless hit by extremely powerful magic. By using this spell you do not even need to use hot clothes in winter.
Base4. +2 sun, +4 for 20 damage
As per Ward vs heat and flames (base 4), dropping the range to Personal and boosting the soak for cold based spells to +20 (no fancy +5 extra soak "just because" as with other fire effects as per the guidelines)
The spell does not allow me to walk in the middle of the blizzard (ReCo4), nor to see/hear through it (CrAu15). However, Molten iron does +12 damage according to the RAW, so I might be able to drop the damage magnitude somewhat if you think a secondary effect could be fit in and still make the spell worthwile. After all, my ignem score will help me withstand cold damage as well, so such ahigh resistance might not be needed. I have no idea what kind of effect would be fitting alongside this spell without raking as an unrelated secondary effect that should be an other spell.
FLAMBEAU PLEASE; NOT WANNABE WINTER FAERIE
I was having breakfast when it hit me in the forehead that the concept is looking more along the lines of the archtypical bright winter faerie than a proper flambeau. Cool, detached, aloof and crytalline. No mud & dirt, no bloood, no laughs, no suffering and self sacrifice, no thrill. No real guts, basically. To me a flambeau ends a combat soaked in dirt and blood (usually his and huis enemies), not looking like a perfume advertisement supermodel.
I think Mark Faulkner will enter a rampage if we all continue to follow this line for the Andorra saga
As a consequence, I am changing the PERSONALITY of the magus, even if not the ice focus. being an ice expert doesn't make you a frigid block of frozen stuff. You can also be a cool guy! (yeah, extremely lame joke, I know. You can stone me now ).
I will be boosting the hunter, thrilling and bombastic aspect of the magus and move away from the detached nature of it. After all, ice giants (magical) have quite a temper in a lot of stories. 
Cheers,
Xavi