It would be great to create also characters with Asset Forge.
well, you sort of CAN... There are primitive shapes that are humanoid shapes... Install them as OBJ files with their own .mtl file, and create a character in a t-pose, save the whole character as a merged .obj file and upload directly to Mixamo from there. All you have to do is envision it, have the pieces for it, and you can build it.
Seconding that, primitives are enough to make a character model. Here's one I made using only primitives:
You could make hands with half-spheres for the palms and cylinders for the fingers, and you could use a cylinder for the neck. With that said, if you wanted to make something more complex, you would have to use something like Blender.
Unless Assetforge evolves the ability the merge faces and calculate intersections, I'm afraid that model's for humanoids - assembled in Assetforge - will never be able to be properly animated. The exported models will be pieces that aren't truly attached. Awesome programs like Mixamo won't be able to use them. This is why I haven't even attempted to tackle making models for humanoids.
I sort of agree AND disagree.... I agree in the fact that you can't just take a figure and throw it in your favorite modeler. However. I DO believe that the base OBJ, once imported into something like Daz, exported back out as FBX and back in, CAN be weight mapped, texture atlased, and have the Genesis rig applied to it.
Also, if someone just wants to create body PARTS, and group them as objects themselves, they could then be attached in a heirarchy in Daz or 3ds Max and made to make one of those multi-part object (sort of like old FF& or Neverwinter Nights...)