Well the thing about materials in general what you are trying to achieve, in this case sub surface scatter, is not always achieved by simply applying a texture to a material slot as the output is more of a rendered shader effect than a rendered texture. so to make something plug-n-play the base object that the material is being applied to needs some level of consistency in it’s construction.
In the case of character development more than the shape of the character is a need for a standard UV mapping solution that is close to identical between each and every character be 1 or 1000.
Since G3 is a framework character then any character using the G3 base can share the same materials and textures as a instanced material or function and would only need to be made once.
An example:
This as a test uses the photorelastic character material provided by Epic and although not that impressive is still rather impressive for a days worth of work 
Lets call it a test of not trying to hard.
Then again.
Getting into more of a personal opinion than fact is that once again Genesis is nothing more than a framework asset available for use on which to build other products. G3 is a sphere or a cube with bumpy bits that what ever you build on top of it as original content or as a derivative is your property to do with as you please. If someone with material skills wanted to could use the available resources provided by Epic to develop skin hair and eye shaders for the G3 base and sell it on Epic’s market place.
Once again though it’s just an option at this point as the ability of UE4 to maintain the fidelity of assets,via Datasmith for example, is a recent improvement to the DCC pipeline and as yet another opinion it’s just a matter of time before the rendered result in DS is achieved in UE4…