I like oven reflow process 
What about power management, seems there is LDO for 3.3VDC device like wifi chip ? With a strong avr 8 mcu (4KB++ ram) you can use RTOS with power management optimization
I may be interested as a very good platform for my ipcam, as battery standalone device with a small lipo, put ipcam everywhere (in wifi range) with a good battery life, seems to be a perfect iot platform.
PCB is two side with home made metalized vias ?