Network design always comes down to a simple set of facts:
A network is an electrical transmission medium with unwavering boundaries created by reflections, spurs, terminations, and the like.
There are transmitters and receivers that must listen and talk to one another, and the more distance and topology that's involved, the more difficult this is to manage.
You must always plan for errors with things such as cyclical redundancy check.
Without standard protocols, everything's a big Tower of Babel.
Don't reinvent the wheel. These days it's not necessary to develop a new protocol because one that meets your needs lives, walks, and talks. You can take it and use it, even if your physical layer is something new.
"If you need a new idea, read an old book."
In this case, sometimes not-so-sexy technologies from the past can come in very handy. There are many high-speed, long-distance, real-time networking requirements where Ethernet just doesn't fit but Arcnet, for example, works quite well.