Well what i have managed todo so far is to use the object file for the mesh eg skin and have that within photoshop, and as it stands it is a full 3d object. the step that is missing is being able to set that 3d object as a static, none interact-able object which i can then store as a system for the .dds files which have there own mesh for stretch, movement etc to sit upon. And thats the bridge im looking for because as it stands the .dds files load in 2d in a basic tailors pattern with the obvious rgb layers and the alpha layer being the mask. But shading and adjusting the pattern is very hap hazard and mainly luck unless your a pro, and working out what part of the pattern joins what at which point is very fiddly.
That bridge is the UV Map. Some meshes already have it, others need to be created. It is not always an easy process. A UV Map take a 3d mesh and lays it out in a 2d shape with the coordinates of U and V where a mesh has three coordinates X, Y and Z.
Once that UV map is created, then you can import the entire 3d mesh into photoshop, where it will see that UV map and allow you to create a texture for it.
If you do not create a UV map or none was already included, then the texture can be applied to the mesh, but will resort to a standard wrap (sorry I don't recall the name of this method at the moment) This wrap can be spherical, cylindrical, a plane or a box. These do not always produce the desired results, but for basic shapes, they work just fine. The UV map on the other hand will force a point in the map to coincide with the a point on the mesh, forcing a tattoo or eye color to stay put and not move (unless the UV map is animatable, which is beyond photoshops capability).
This UV map can be created in Blender, Lightwave, modo, but not photoshop.
As for 3d formats, I highly doubt that photoshop will support majority of the 3d formats on the market any time soon. Simply because it lack majority of the features the rest of the market already has. Maybe one day, but not soon.
Bryce from Daz3d.com can import/export a wide variety of 3d formats as well as blender. Both of which are free. But generally these formats are modeling/animation formats, not game formats. Most of the game formats are proprietary (owned by the creator of the game) Which makes it very hard to reproduce, both physically and legally.
As you have mentioned milkshake, I believe that supports a wide variety of game formats. I never tried it, so it is out of my league. Since games are their business, odds are greater they would have a wide variety of game formats (that's my conclusion anyways)