Ok, i utterly failed to create a material, that can combine 3 separate transparent materials, of which each has it´s own IOR in UE. ^.^
So atleast here is the effect i hoped to achieve rendered with Cinema4D: One gem rendered 3 times with 3 different materials (one for each color, and each color with a slightly different IOR), then the layers got combined.
And as expected, you get your chromatic abberation, and it is slightly better, because of how much the 3 colors gets separated, now also depends on the material thickness and shape.
The 3 layers, and the Gem, if anyone want test it with UE. Maybe one of you can create such a material 
OR Epic could just decide to give us an IOR input, that can compute a complete Vector3, and not just the first channel from a Vector3 
Gem.fbx (332.4 KB)