Well, not specifically argueing against you, but using this as a springboard, I think you can't really do it right. Kerrigan, like Arthas, isn't the kind of Character who should find salvation in any other form then a slit throat. It cheapens them. The idea behind the two is actually pretty awesome and original literary idea applied to video games, though it is cheapened by the fact that blizzard does it twice.
They were both corrupted more or less not entirety of there own volition. Neither Arthas nor Kerrigan became who they became through a gradual corruption of a flawed personality. They cause there own damnation, yet they are not the ones responsible for it. Arthas did not chose to become a tool of the Lich King and lead armies of genocidal undead against his homeland, nor did Kerrigan chose to become infested.
However, they are also not tragic heroes. Ultimately, both of them eventually embrace there power and roles as killers and monsters, both of there own agency. The centerpiece of their stories is not their downfall, whether Arthas's arrogance and hubris, or Kerrigans ruthlessness and a "cursed" genetic fate (she is a Ghost, abducted from bith). This would cast them as tragic heroes.
Instead, the centerpiece of there tragedy is ultimately there embrace of evil. Kerrigan, freed of the overminds will, chose to slaughter and burn, while it is implicit that Arthas comes to enjoy his damnination based on his Dialogue. He clearly displays some level of free will, as shown by his arrogance and initial disdain towards other servants of the Lich King of equal rank, like Kel Thuzad. So when he commits these acts of wholesale genocide, he should be tortured, in which a redemption could be a fitting end. No, rather, he enjoys them. Or accepts them, at the least.
By redeeming them, it cheapens the centerpiece of there tragedies, that ultimately, jaded and corrupted and used by malicious, and near godlike powers, they chose evil when they had a chance, independently, to harness there own redemption. They did not.
Thus, they should not get it. Blizzard shouldn't destroy the centerpiece towards that plot.
That being said, perhaps I was argueing a slightly different point. Actually, kerrigan being partially de-infested would make a great set up for Heart of the Swarm where she struggles to regain dominance. Rather, what I was argueing against isn't the semi-irrelevent plot convention of de-infestation, which doesn't really matter, but what de-infestation represents, redemption.
Kerrigan and Arthas are not tragic in their corruption, they chose there corruption. If they do find redemption, it should only be in death (which blizzard does quite well with Arthas's death. The lines were cheesy as hell, but the overall motif didn't cheapen WoW's lore at all)

