tools are nice prototypes 
Skookum Script is much more advanced, half-way to its own scripting IDE in the editor. Still not integrated into vanilla UE even after Epic purchased the company behind Skookum Script.
It’s simply no solution available out there could be considered as “first-class citizen” in the engine. A new text language should be designed to a sweet spot between C++ and Blueprint like it would be there since the beginning of UE4. With changes to Unreal C++, blueprint VM, blueprint nativization, text-based assets.
Such language should hide Unreal C++ things still cumbersome for less programming-oriented people, like managing includes, linking modules. Perhaps some nicer equivalent Unreal C++ of delegates, macros, etc. And it wouldn’t crash on the invalid pointer (that’s what you have in managed languages, blueprints or C#) - as the person before you said. Basically, it should be a text-based blueprint, it should feel like home to people used to blueprints. A place where programmers and non-programmers would meet and cooperate. In projects with a team of programmers, we have tools and systems written in C++ and this used by the rest of the team (via blueprints and custom editors). These environments don’t mix.
And it would be great if it would take one step further, make new language easy to write multithreading code for advanced users/systems. Currently, the blueprint is trapped in a single thread basically. It’s not a trivial challenge even in C++, due to the engine’s architecture. Everything is OOP in a gameplay framework, not easy to use efficiently like 16 threads for gameplay of new consoles.
If we gonna have the 3rd language in the engine (Unity has only one exposed!), this needs to be so good, that everyone wants to use it. Easy to jump between all three forms.
C# wouldn’t solve it nicely, it would be just an alien thing, programmers would often entirely ignore it and continue with the current workflow. C# would be just eating a painkiller while sick and pretend it’s all good.
So just placing nodes with text-based code in blueprints is nice, but I would expect much more from next-generation scripting language