Nice to hear that you like Orbi.
Unfortunatelly, I do not plan to convert to FF.
While I really like many of the additions, othere I do not, so I will stick to FfH as a base. But mostly, I do not have the time to convert and then balance everything on a new base...
And now to specific suggestions:
Mechanos - they are not really finished and I agree with your suggestions. In fact, my main inspiration was Arcanum, together with WH 40K. Unfortunattely, there is not much art fitting them and I will try to make some of my own, but that takes time - and I am busy with other fixes... But I promise to myself to work on them soon

I want mechanos to be a civ that when encountering a big demon, just carry a bigger gun

Power - now that is an idea...
Religion in cultural values is completly different aspect of well, religion. It just indicates that religion is really important for the society, while religion category just adds some religion-specific effects. Combination of religion and neutrality/humanism is a bit weird, but that is not the only such combination, plus I do not think I would like to use religion civic with them
Serfdom - is it really so overpowered, people? I rarely use it, prefering guilds. But if you do think it is too much, I will drop it to 10 or 15 %