I have a pair of queries for an ice based magus.
Would Ice be a suitable subject as a minor magical focus. Could i up it toice and cold, or would that be more of a major magical focus?
Are the base guidelines for creating ice identical to those for creating water? I know they use the same arts Creo Aquam, but do they have the same base levels? IF not, what do they use?
1 => Ice is a good minor focus, IMO it is perfect in terms of how much it affects (part of Aquam, using several techniques). Cold might be its own minor focus, definately not to be combined with ice for a minor.
2 => (Serf's Parma) My gut feeling is to add a magnitude to the base for creating ice vs water (a bit like with Terram). It does more damage if you're interested in that, so it should be a bit harder to cast.
Cold is suggested as Minor Magical Focus in HoH Societates [pg 28]. Ice is much more versatile however, and thus might qualify as a Major Focus. Ice and cold spells are thematically similar enough though that I'd seriously consider granting "Cold and Ice" as a single Major Focus. Since the proposed spell types employ completely different arts (Creo/Rego Aquam vs. Perdo Ignem) there is less opportunity for the player to exploit the dual-foci than might otherwise be the case.
The only specifically Ice-based spell guideline I've found is a Creo Aquam one to "create ice in a natural shape..." (HoH: Societates, pg 34). However, that guideline looks very similar to the "water" guideline of equivalent level in the core book. Therefore, I'd allow my players to use any (applicable) Aquam guideline with ice as well as water.
Ice is more versatile than cold? I'd be inclined to think the other way around....
Double posted 
I don't have A&A yet, so I don't know all about any cool, warm, dry, wet applications, that may have been introduced in that tome, but using the guidelines for assessing the value of a magical focus, I consider ice the more versatile as it could be used with any any combination of techniques + aquam and can be used to create any number of useful items - bridges, walls, castles, stairs, daggers, shackles and more.
Cold spells are very useful and as described in HoH: S can affect many targets with a single form/technique combo, but the narrower range of effects applicable to cold leads me to consider ice the more potent of the two foci.
sincerely,
Gremlin44
I played a Flambeau maga with this kind of concept.
I had "Create Ice and Cold" as a Minor Focus, the group deemed it narrow enough to only be a Minor. After all, there is a limited number of PeIg cold spells to use, and quite some more Ice spells - but you'd have to be creative. I ended up with a lot of ice-missile spells, a single "create a shield of ice for deflection", and a single "create ice structure" spell. Also 2 weater/snow type spells.
The additional Cr and Re Aq guidelines in Societates list uses for ice. I think we only added magnitudes, if the ice needed some unnatural properties, such as remain longer than it ought to, due to ambient temperature.