I think I might be possible to attache a serial interface to the container. I did this for USB devices with success. As I do not own a serial rotator I cannot test it. I built a working rotator using an ESP32 modul and some code I wrote. I will directly be fed from the satnos docker container I run. What motors do you have attached to the arduino board? You can have a look at mine here. I can share the code if you are interested. It is not very beautiful so.