Thanks for approaching this problem in what seems, at least to me, to be the right way! My struggles with a Packer -> Vagrant -> Ansible <-> Win10 virtual box only yield mediocre Windows build results, and it’s great to see you’ve laid a solid foundation for a proper Dockerized pipeline. I think I will find your ue4-docker and conan-ue4cli projects to be quite useful 
I haven’t looked at Docker for Windows in a while, but I see there is now Linux Containers on Windows available, so that both container flavors can be run side by side. Jenkins is going to love this!