A proof of concept (i.e. Multi-Drop Remote Bootload) using avrdude with an xboot serial boot-loader (note optiboot also works).

http://rpubus.org/Video/14145^3_RPU_RemoteBootload.mp4

The proof of concept used Host2Remote* firmware on a RPUftdi^3 and i2c-debug** on its MCU board (OSEPP Uno R3 from fry's electronics). The remote device has Remote*** firmware on a RPUadpt^3 board mounted on an Irrigate7^1 (which is an ATmega1284p with xboot). The firmware bootloaded onto the Irrigate7^1 is BlinkLED****.

* https://github.com/epccs/RPUftdi/tree/master/Host2Remote
** https://github.com/epccs/RPUno/tree/master/i2c-debug
*** https://github.com/epccs/RPUadpt/tree/master/Remote
**** https://github.com/epccs/Irrigate7/tree/master/BlinkLED