My bad, usually looking up “RJ45” gives me more of what I’m looking for than 8P8C. I wasn’t aware that 100BASE-T1 was a 2-wire Ethernet standard, that’s quite handy.
In that case, assuming non-8P8C connectors (JST PA or Molex CLIK-Mate would be good places to start) the biggest hurdle to clear would be that we would still need miniature network switches and PHYs on each device. At that point, I would sooner run a bunch of RS-485 or RS-422 busses, which would be much cheaper to implement at the cost of proportionally reduced data rate. A 10Mbps RS-422 bus can still be up to 30ft long, and low-power devices like sensors could run at reduced data rate to save power.
As it is, we run robots on a 1Mbps bus, with Ethernet only being used for cameras. I could see that being the primary driver of a need for a faster bus, but I’m curious what tangible benefits people see from running a bus that’s 100x faster.