Hi, Nemik,
At the beginning our design is put the Arduino inside the PCB. But we finally design to remove it because:
1/ It is hard to do the determine the pin configuration for different applications.
2/ developer may need to change slightly Arduino part hardware to adapter for different enviroment.
3/ Compare with designing a full feature product, the development for the Daughter board is easy and have a short lead time, low cost.
4/ The Dragino will limited to the AVR MCU while use modular design. It can be used for other MCUs like PIC, STC.. etc through a short development time. what to do is design a module as well.
We think modular design is the best way to spread the open source product and will highkly reduce the development cost and time on release a new product. This is very important when you have a new product concept and want to test the market before manufacturing them in volume.
Cheers ,
Edwin