Re: Positional/physical addressing

I have a large group (hundreds) of switches and displays.
Their state needs to be determined/updated rather slowly
(a few hertz).  Each has local smarts so it can retain
some state information and processing capability.
 
Their physical arrangement varies from one installation to
the next.  So, there is no economy of scale available by
"settling" on a specific configuration or physical arrangement.
 
I would like to be able to address them (the entire *set*) -- and
pass data to/fro -- with a small, fixed number of conductors /having
built them all identically/.  The amount of data exchanged being
traded off vs.  update rate for a given interface bandwidth.
 
The obvious "one wire" scheme would have a gazinta and cumzouta
for each device so the device could modify a serial bit stream
to account for its "position" in that stream.
 
I can pipeline processing between devices so the overall access
rate remains high (though latency obviously suffers).
 
But, a single device failure renders all downwind devices
inaccessible (or, possibly ALL devices, depending on implementation)
 
I'm looking at a two wire solution that piggybacks the data
stream on power and ground (those "two wires").  But, it
adds complexity to the devices (I want to keep them REALLY
small and dirt cheap)
 
Any existing schemes that allow this without the failure mode cited?