You're not edging in at all! Meta reflections are fun. If you would indulge me once more, here is a clearer explanation of my thoughts:
JKR seemed to attach such importance to the four elements in the books that I thought this might be an interesting method of providing a loose kind of structure. The forest seems to function as a landscape of disorientation and orientation (finding the sword), as the theater of rebirth (Voldemort sucking blood from unicorns) and death (Horcrux!Harry at Voldemort's wand) in the books. Water is also incredibly important - from the Chamber of Secrets to the Black Lake to the pond in the Forest of Dean to the sea of Inferi guarding Slytherin's locket - being particularly associated with Slytherins. Snape could be compared with water himself, given his tendency to lie quiescent, then come to a raging boil - given his innate sneakiness and ability to adapt. Of course, water is transparent, whereas Snape is THE most intransparent character in the books, the one character whom everyone seems to read incorrectly. This is why I like associating him with fire as well. And Harry, the Seeker, the Master of Death, didn't seem quite complete to me without reference to the lightness of air.