My two cents:
Rather than changing "stances" with PhaseChange, as it were, I believe integration of different effects depending on the kind of source used is better implemented differently. From a design perspective, it'd be more user-friendly, simple and elegant to have moves do a set something by default. For example, Surge used on water and ice would always be the normal Surge, whilst using it on specifically either a snow block or a snow layer transforms the ability into one that uses snow.
Partially, I think, these changes would mostly be aesthetic in that abilities would be snow instead of water or ice for the sake of continuity - which is fine, because snow behaves differently than water or ice (can't see through it, can't walk through it, won't put out fire, etc.) which in and of itself brings new tactical options. If, and how certain moves change in functionality depending on source used is something that would have to be discussed separately.