How to select the most appropriate (serial) bus for controller?
The physical portion of your network could easily be RS-485.  Although one normally uses termination resistors on all of the stubs, this can be alleviated by having the termination resistor permanently attached at the longest (furthest) node of the bus.. 

Or - operate at a sufficiently-low speed that reflections are not an issue and thus do not require termination. 

You will need to work out the communication requirements and write your software accordingly.

This can be hot-plugged provided your software is written such that it will tolerate the momentary disruption