I'm hoping to hear from the development team about both the gameplay implementation and the lore of magic, because I don't understand why you made some of the decisions you did with your implementation of magic, and your in-game descriptions of magic.
Firstly, why spell ranks? The skyrim engine already provides a robust system for increasing the power of spells based on relevant magical knowledge. Spell ranks seem like a worse solution, with four side effects - only three of which I think are likely intentional. They act as a money sink, similar to buying new weapons, they keep mana costs relative to player mana in a relatively narrow, well balanced range, they act as a way to punch above your weight should you luck into finding them early, and they clutter the spellbook to a nuisancesome degree.
But their role in keeping mana costs fairly constant could also be achieved by decreasing the cost reduction offered by enchantments and skills - total mana will still increase, but it is a smaller factor than the time taken to regenerate enough mana to pay the absolute cost of a spell. Their role as money sinks could be replaced by changing the cost of skill training.
And personally, I feel strongly that no two spells should do the same thing. A game does not need multiple spells to do damage to a single target, unless there is a significant gameplay difference between them. Attack speed, projectile speed and arc, AoE, ability to chain between foes, knockback et cetera are always gameplay differences, whether a foe has 1 hitpoint or 1000, where raw damage and elemental typing only make a difference if they change the total number of sucessful actions needed to defeat a foe.
The same logic can be applied to weapons, where attack speed, armour penetration, weight, range and one-of-a-kind enchantments can be used to provide fewer linear upgrades and more interesting sidegrades, and probably should. Differences in kind are typically better for gameplay than differences in scale.
It would be more interesting, to provide a hypothetical, to provide the player a straight shot firebolt, a fireball thrown in an arc, and a short ranged shotgun-burst of flames than seven or eight different magical damage types all used in the exact same manner, and only switched between to hit the weaknesses of specific foes.
Secondly, some questions regarding the naming of the schools - Why Mentalism and Psionics? The words mean more or less the same thing, and while the mind affecting magic of psionics is aptly named, the school of mentalism provides self buffs that, in terms of gameplay, affect only the flesh. Why Elementalism, or rather, why change destruction to elementalism when the elements are still used exclusively to destroy? If the magician sculpted weapons and armour from ice, of used fire to cook or extract metal from ore or even provide torchlight in darkness (much less frighten wild animals, change the temper of metals, imbue nonmetals with the temper of metals, act a a symbolic dividing line between man and beast and a visual shorthand for enlightenment, create smokescreens, provide defence against frost etc.), the change in name would have some purpose, but as is, the elements always just destroy stuff.
- the explanation given in game for arcane fever and magic in general? Arcane fever seemed really promising. The idea of power just eating away at you from inside unless you control it through self discipline and sacrifice is really cool, and is what finally sold me on your game. But the actual explanation isn't that there is power inside you. It is that there is power in other realities, and being bad at understanding other realities hurts your brain so much you go crazy. I understand the idea of making magic pseudoscientific. People have done it well. Actual alchemists and other early scientists did it very well, because they documented physical phenomena and ascribed them symbolic/mystical causes, then extrapolated sybolism based laws of nature/magic from those mystical forces they "observed". But I digress - I just personally don't really like the "you go crazy because you are bad at understanding the many worlds theory of quantum mechanics" angle, especially when the gameplay does not reflect it. The lore example of a fire spell, a version of reality where a man's beard just happens to be on fire, does not match the gameplay example, where you make fire from a metaphysical fuel inside you and throw it at the man's beard, then the man's beard catches fire. In one, the spell begins and ends in contact with the man's face, traveling between worlds/probabilities, but crossing no physical distance. In the other, magic starts within the magician, leaves the body, travels through the air and flattens the other bloke's nose.