Isn't there a converter for V3 skins to Posette available? There are a number of converters out there. Surely there is one for this task? Maybe from V3 to V2, then from V2 to Posette... something like that
There is a Daz converter but obviously it doesn't work for non commercial products like our beloved Posette... You've a cheap solution: use the Nea character from narcissus, she wears V2 texture as default... So I think that with the Daz converter... Maybe