In the process of creating a Display helper, I've also started some refactoring work to remove the KernelPipelineContext and replace it with a hopefully more understandable KernelCommandBase.Handler method. Similar to the way ASP.NET Core middleware works, this Handler is assignable so that the kernel can make decisions about how to implement the given command. The handler has access to the KernelInvocationContext in order to raise events much like before.

I'm considering additional changes here to replace the OnNext / OnCompleted / OnError methods on KernelInvocationContext with something more specific to the use cases here.