A few notes here, Ice is composed of water but coldness itself is often asociated with air, the reason may be, one of the effects of cold is that it slows down; and slowing is the negative of speeding up, and speeding up is the domain of air.
Technically, it's actually the other way around. One of the effects of things slowing down is coldness
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I personally always use ice. Its simply my favorite element and in every game with spells I tend to use just ice spells just from the principle. And one thing I dislike is, and I hope it wont be in Elemental, having ice spells in two schools of magic. I am pointing at AoW:SM here especially; a majority of spells involving ice were in the Air sphere, but certain spells (mainly quite important Ice storm) were in the Water sphere; and by doing Cosmos and merging Air with Water, you couldnt reach Ice Storm with water levels and have other level 3+ ones in Air. That sucked.
I'm kind of hoping you don't have to choose your mastery at the start of the game. I never liked having to determine so precisely the nature of my end-game wizard or channeler or whatever you want to call it. I didn't play MoM much but it always drove me crazy in AoW. I want my channeler's proficiency in the various schools of magic to depend on my in-game choices, not on a setting a choose at the start of the game. As my channeler gets stronger I want to be able to improve his proficiency in the different skills, not just research bigger spells or cast more per turn. In AoW I never really got a sense of my wizard's power increasing much with time. Yeah they get new spells and they start to do a little more damage, and I could cast more per turn, but it felt so impersonal.
I want to be directly involved in shaping the nature of my channeler throughout the game. I also want it to be more open-ended than in AoW. There you could allocate six spheres to whichever masteries you wanted and that was that. But if I'm playing on a big enough map that lasts long enough, I don't want to be so artificially limited. I want my channeler to be able to master, or at least to become very capable in, as many schools of magic as he has the time and skill for. There should be trade-offs of course. For one, if I choose to invest in becoming a better water channeler in addition to my expertise in earth magic, then the spells of my rival who has focused solely on earth magic should be more powerful than my own.
Basically, if I'm playing on a map that takes a month to complete, I want my end-game channeler to be able to be an all-powerful earth mage who can cause a massive world-wide earthquake capable of completely altering the geography. But I also want to be able to create a jack-of-all-trades channeler who is very powerful in many different schools at once, yielding greater versatility (including spells that draw from multiple schools) at the cost of raw power in any one school. Such channelers could still cause world-wide devastation, maybe on an equal scale, through a smaller selection of spells that draw from many schools at once.
Another thing I noticed in AoW is that I almost always ended the game having researched every spell I could. I'm hoping that won't be the case in Elemental, at least unless you're playing on a really massive map. I also hope that even if you run out of spells to research, you can still improve them in some way.
Long story short, if there are actually to be a dozen of ice spells, do not split them up in two like in AoW:SM. Either create a separate element, or make combining of elements in such a way I wont be restricted.
The thing is, if im going to be ice mage, Ill be having some degree of water and air mastery; so technically I will be "fluent" with 3 magic paths; water, air and the related ice.
I'm all for that. The freedom to create the channelers we want, not artificial limitations!