Hey Razorfield,
UE4 4.8 now has an experimental feature that will create specular highlights on Translucent materials.
Steps to Recreate:
1.) Create a new Material
2.) Add a base color that will show specularity well, IE a saturated blue.
3.) Plug in a Constant value of say, .5 into specular.
4.) You can add a normal which usually works best, nothing too noise just enough to reflect the specular map.
5.) Change your material Blend mode to Translucent
6.) Scroll down under your Details > Translucency options and click the box for Screen Space Reflection
7.) Under that same Panel Change Lighting Mode to Surface PerPixel, this feature is experimental.
8.) Lastly by pressing the ~ key enter the command r.ForwardLighting 1
This will allow for specularity on the surface of a translucent material.
Enjoy,