Cleon
Legend
Yes, something like that seems familiar. Tsochars from Lords of Madness can infiltrate a host's body, but that's more like dominate. Yakfolk, too. Maybe hellwasps?
Well, the original description says it works like polymorph other, including the duration, so why not use the 3E equivalent spell as a basis?
Something like:
Skinstealing (Su): If a windigo personally kills a humanoid opponent, it can wear the corpse's skin and assume the form of its victim. Skinstealing is a [full round?] action, and the windigo must steal the skin within [1 hour] of a victim's death. The windigo gains the physical abilities of its new form as per the spell polymorph [or as per the Change Self ability?]. A windigo can retain a stolen form for [X minutes], after which it tears through its victim's skin and reverts to its true form. [It also reverts to its true form if its stolen skin is ripped by the windigo taking more than Y points of damage from slashing or piercing weapons?]