Thats sounds excatly what im looking for.
I've worked with RS485 quite a bit, but only in a commercial building automation level - i never had to figure out the parts to make the devices.
The way most of my older controllers handle the communication ( which is half duplex 485) the that the " master " holds a token "a virtual point" which allows it to talk - when data is requested from a slave the master sets the "token" on the slave, so that the slave can talk. Once the master receives the reply the master disabled the slave token and is free to broadcast another request.
I dont think it would be terribly hard to recreate that process in this format
That is what Im going for here, a home automation system that would be completely open source yet more flexible than what is currently offered