@JamesC, @Borroz I agree with both of you 
I was not saying that the Microchip RN2483 is too expensive, I think it is the best (only) bargain that gives you a complete LoraWAN stack and RF certification. I think it is just a challenge on its own to build the lowest cost node possible. And indeed that will only be useful for 2 groups: the tinkerers and the corporate people who expect to build 1000's of nodes.
I guess that also with a RN2483 you still need some RF certification for your product? AFAIK you can still set the duty cycle of the RN2483 to a value that would be "illegal"?
@BoRRoZ About low power consumption: like I mentioned I think your approach is interesting and we won't be able to achieve that with an ESP8266, I hope ESP32 will have the right low-power features to achieve real low power sleeep (It does have more low-power features but didn't investigate this in detail yet). For certain nodes where very low power consumption isn't the biggest issue a relative powerful but cheap uP like the ESP8266 might still be usefull?
Would indeed be great if the full power of the RN2483 embedded PIC18F46K22 would be usable (e.g. for serial protocols) the same way Espressif has done for their ESP8266. Then you could build a complete solution with the RN2483 only and no external uP would be required. As Microchip did provide a complete set of GPIO's on the RN2483 it would indeed be a logical next step 
And nice links from @IOT_Marco, looks very interesting!