This has to be done in C++, if you want it to be a widget thing, because you need to write a custom compoundWidget class in slate, which gives you access to FSlateDrawElement::MakeCustomVerts().
I am currently developing a radar chart like that, that also works with animated materials and multiple value layers.
When I’m done, I’ll put it onto the forum for free.
Nearly done, just wrapping everything up and do some adjustments. 
