Writing an off-shoot of this thread since there's another version of the game built by a different studio on an entirely different game engine:

 

This version of the game was created by SCEE London Studio sometime around 2008-2010(?) and is created on a heavily modified version of the singstar engine. There are also references to an EyetoySDK found inside the game assets.

The .model format they used seems straightforward enough with there being close to no compression or encryption at all other than the entirety of game assets being stored in the usual London Studio .PKF package. The characters skeletons seems to be stored separately in the .skel files, but I haven't really figured how that works yet. There's also the .resource and .scene files that's basically just a renamed .xml files containing a list of external resources like textures and shaders the model uses.

Although I've made some progress figuring out the individual mesh group offsets via model researcher, I am unfortunately not well versed enough in 3D model reverse engineering to figure out stuff like bone indices, skin weights, blend shapes, or even creating an actual import plugin for blender. Any help with the creation of an importer or conversion tool would be much appreciated.

I've attached the link to the publicly available beta build of the game and sample folders of both character and environment assets below. 

Build link: https://hiddenpalace.org/Until_Dawn_(2010_demo)

lori.zip pilot.zip

Work in progress

Here you go - plugin for Blender 5.0
Imports meshes, skeletons, animations and textures
Some animation files may fail to import (could not figure it out)

io_scene_until_dawn_demo.zip