This board was built after three iteration of the same kind of board without usb serial converter (much like a arduino mini). This board can be seen as a dev board while the version with no converter is much like a production board. The cost and size of the PL2303SA does not affect the BOM too much but will increase power consumption. The PL2303 consume up to 450µA when there is no serial communication going which is lot compared to the esp8266 80µA deep sleep current. The PL2303 can be disconnected from the 5v supply to minimize power consumption. If no serial communication is needed, the PL2303 can just be not populated, and the board can be programmed through the headers. A resistor can be installed accross the D+/D- pads of the USB port for a charger to detect it.
The goal was also to have the ability to use a cheap power bank for supply but the some power banks needs a minimum current to be drawn for the boost convert to work.
The board worked right after soldering. The PL2303 was detected immediately and i could program the board through the Arduino IDE. This make a very convenient tool to develop