Point of information, years ago I participated in helicopter icing test involving the -53 and (no kidding) a UH-1 with pneumatic boots on the leading edges of the blades.
The boots worked well enough as I remember but they didn't stand up to abrasion well enough.
The CH-47D has an unused generator pad on the aft transmission (last I saw one it was unused) which was intended for hot blades. A few of these blades were rumored to have been produced before someone decided they weren't needed. I have two personal experiences of contradiction to that decision. Unforcast, I swear.