I just want to mention that I created a Docker image with a full system virtualisation with qemu. So OpenWrt is runnning with its own kernel inside a virtual machine and everything is packed together in a Docker image. I hope this approach overcomes the limitations when OpenWrt uses the host kernel.
You can find more details here: https://github.com/AlbrechtL/openwrt-docker. I also started a new thread here: OpenWrt Docker Image (experimental)