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