Real time render engines optimization
You need to avoid innecesary resouces for a fast loading. I mean to innecessary resources such as innecesary bones, uncombined meshes and about textures, independently of the size of them, try to minimice the number of these, because they are calls that the rendering engine will need to make at load time.
This character only take 25,000 tris and 512 x 512px textures for the face and prop (helmet) each other and 1024 x 1024px for the suit and armor respectly, it really is less texture size than one 2048 x 2048px. but are separate textures because share it with other characters, also skin and hair are separate for to change it independiently for differents versions, you can see more Human soldiers
The above characters, both, female and male version, share the same texture files, the face and hair is not possible, of course, this way we reduce the number of calls each time the engine needs to load a character.
And pls, you use LOD for reduce polycound and texture sizes when the character is far o when the character is very closer to the cam, for example when the palyer change to first person view.