Have slave/master in I2C ?!? Not sure it will be the easy or appropriate way... a simple RS485 network will do the job.

You can place up to 8 I2C device on the same pair of wire if they have the capability of. The only things you have to do, is to change their A0-A3 setting bits(kinda chip select) to access them separatley and have the according Control Word to access them.

I've never see any application for this I2C_slow stuff. All i2C that i use support the high speed communication.

To resume, in your case, i'll prefer using RS485 network ICs + all I2C device you have on the same pins.. if they supported this.