My aim was shrinking the Arduino UNO to minimum size by simultaneously maintaining it's fundamental functionality and pinout.
The result is the ShrinkDuino UNO with ATMega328P and CH340G as USB-serial interface - well known from other Arduino UNO clones.
With a size of approximately 4.3 x 2.2 cm (without USB plug) it fits direktly to the USB port of a PC.
You can directly plug it into the USB-port :) And the pinout is the same like on Arduino UNO. That makes it easier to wire UNO shields to it. Admittedly a disadvantage are the missing LEDs for serial RxD and TxD.
I see. So from the practical point of view, I would need to get under my desk to plug it in, and I can't plug it into a breadboard because of the weird UNO half-pin header spacing.
Nobody said it's the perfect solution for everyone. But for some of my projects it's more practical than wiring an UNO by USB cable. Maybe it's because I don't use breadboards and I mainly use my notebook instead of a desktop computer.
What about connectorless USB PCB plug ?