Today I had a closer look to these sites that introduce DIY Zigbee devices and noticed something right away: the author uses the same Zigbee module as I am (E18-MS1-PCB from Ebyte).
In the past I've tried to look for projects or information with this CC2530 based module but didn't find much but I thought it could worth another try since someone is actively building Zigbee devices with it.

As usual I used my best friend Google. With the keyword "E18-MS1-PCB" I went right away to "Images" and just after a few scroll down this caught my attention:

I mean... the image title speaks for itself, right? With really high hope I clicked that image and jumped to Z1 Mini Development Board lets you build custom ZigBee end devices. After reading the article, there was unfortunately nothing new on the horizon. To be sure, I had a look to the linked Wiki page and there I saw this:

Great firwares? For the CC2530 chip... For a second I thought these firmwares could be the ones of those DIY Zigbee devices I mentionned earlier. Or maybe ready to flash firmwares to use a CC2530 as a ZNP device?

Well it turned out to be far BETTER than that: A GUI tool for creating your own alternative Zigbee device with a flexible configuration of inputs and outputs.

This sounds so promising and it might be the solution I was looking for to easily make a Zigbee device to enable connectivity of my air conditioner with Home Automation. Gonna spend this Golden Week holidays digging into that.