I2C differential network architecture using PCA9615
You'll find that modern cars are essentiall 2.55m × 3m robots containing a human driver.
The guys producing millions of them have agreed to use CAN, because the combined cost of cabling + CAN-capable controllers + connectors is cheaper than the effects of having the unreliabilty of rolling something based on I²C or their own bus inventions. Use CAN.
Low-Speed CAN is specified to work in star topologies, or mixtures of stars and long buses:

Figure by EE JRW
It works over the cheapest of all data cabling: 120Ω Twisted pair, aka &quot;cheap network cables&quot;. The fact that even shielded network cable with high bandwidth is cheap is undeniably a large plus in applications with multiple motors in large devices that might even see RF ground differences.
CAN-capable microcontrollers cost 2€ in single quantities, so I'll go with: if you need to connect I²C devices, keep I²C short and linear, and connect them to such a microcontroller close to their position, and then connect that via CAN. This, by the way, also isolates faults very effortlessly, and makes writing a controller easier: your central node can issue &quot;high-level commands&quot; to the CAN microcontrollers (like: Drive the motor until you hit the stop switch or temperature increases beyond 80 °C) instead of having to do a load of I²C commands centrally. Makes debugging easier, and atop of that, easier to mentally divide development workload – you know can be either in the mindset &quot;low level hardware driving&quot; or &quot;high level control design&quot;, but don't have to do both at once. You can even have a set of &quot;CAN node&quot; engineers and a set of &quot;control engineers&quot; and they only have to agree on a simple set of commands. Yay!