Just randomly throwing in my thoughts ...
I do not think SoSac should become a permanent. Then it just becomes a 2 turn dimensional shield, and that gets stale. The game need more varieties of defense than permanent based systems. The status-based spell defense of sosac was an innovation, and only really needs refinement, not a backwards transformation.
I totally agree with you, inflicting damage to oneself and one's quanta pool should yield greater advantages than just setting up a permanent for a defined quanta cost. SoSac does this nicely by guaranteeing near-immortality for the following turns (with some soft and an upcoming hard counter), and this will fortunately continue in 1.30, even after the Purify buff.
I like the target both players and creatures but I do not see the thematic sense in making purify remove sacrifice status.
I made up the following explanation for myself: The "sacrifice" you make is indeed an unholy one, instead of bringing glory to the world of elementals by growing stronger and stronger, you stab yourself and give up most of the life-saving resources. You start a gamble like "I bet that my opponent will damage me by more than 40/48 HP". All this is somehow against "nature", therefore the shard belongs to the
element. Look at the optical effect, it reminds me of a somehow flawed soul (don't know how to express it in better terms). By purifying, this "suicidal/unholy/gambling" state is removed and you return to a normal existence again. Well, as long as your opponent doesn't defeat you immediately after that ...
How romantic ... 8)