I get you point.
What I find strange is to see people making tutorials and managing to import shape keys to UE4 without addons.
The are still things to verify, I will check that further.
To be honest, I don’t feel comfortable at all with the idea to make a custom function. C, Java and OOP are kinda far and I don’t know C++ plus the need to familiarize with UE engine… gosh… XD
[EDIT]
More I think about it, there’s something that can lead to a missunderstanding. What I wish with shape keys is to add some kind of deformation range (I can manipulate in UE4) rather than an animation.