Well, it looks like Epic is kind of FOSS fanatic since the engine’s source code is publicly available. This says exactly “the code is there, why don’t you do it yourself” 
And I don’t see a reason to “attack” another user because he points out.
Middleware owners often manage this kind of integrations. Look at Wwise, Substance, Houdini or Speedtree. AFAIK even Steam Audio is updated in form of pull request from Valve.
And yeah, Speedtree 8 comes to Unreal year and a half after Unity… That sucks, of course.
I wouldn’t expect or even demand this kind of integration from Epic directly. Especially that Watson would very well as the official IBM plugin, like in Unity.
Why don’t ask IBM also?