This whole RS485 thing has already been worked out. No hardware multiplexor is ever used. Just a clean protocol describing the conversation between a master and an addressed slave.
The OP is asking about a scheme to auto-assign station addresses to nodes on a bus, presumably such that the station addresses are mapped to the physical ordering of the bus.
I've used a similar scheme, and it can certainly work. You should be able to use just about any analog switch, provided the cumulative resistance is not too high and the switch is sufficiently protected against harm. Another option is to run a separate IO line out from one node and into the next, so once the first node in the line is addressed it asserts the signal to the second one which starts its address negotiation, etc. I think mikeselectricstuff used this scheme on his massive wall of iPod LCD project. This can be just a regular digital IO--in fact RS485 is probably overkill for your serial link. For 115kbaud over 2m, you'd probably be just fine with regular TTL serial unless the environment is especially hostile.