I hear what you are saying, but the notion of MW switching using her false teeth as the different mantles sounds soooo awesome.
I agree that does sound awesome, and the idea of her as some aspect of death, or at least some how the inspiration for mortals to create this avitar of death does sound awesome. However while the name of Death does fit for MW, it's not even close for MS and she did say 'our' so the name has to fit both, and just saying life and death are two different things is both a cop out, and two DIFFERENT names.
Kringle did make a comment that lots of immortals run around wearing other masks or mantles on Halloween night if that's what you're after (and Bob made a comment about how masks on Halloween for mortals mean that immortals can't be sure that it's not another immortal under the mask).
I'm still not convinced that the mask of kringle isn't just that, a mask that Odin wears sometimes. Maybe he oly ever interacts with Fae as kringle so as to be involved, but not intruding, that would fit with the WoJ about how the King of Winter being a wlyd fae that just interacts without staking territory. He has a certain power that he brings to it (thus granting him respect from the fae), he doesn't get involved with their power struggles (cuz he's mostly retired god, so he don't give a ****), he is undeniably related some how to winter in one way or another, hell for all we know waaaaaaaaaaaay back when he and Mab were actually related back before he and she both became what they are now. I mean hell maybe he's her Daddy or something (think about it, can you imagine the man who would survive getting down with Mother Iron Teeth?).
Or really scarey thought, maybe all the old immortals, are family in one way or another. Like the old gods and such creatures are all related some how. I mean I know the red king was only the way he was because of a powerful spirit from the nevernever that had like infected him or something, but still godly powerful and such.