I did indeed partially use your reflection, I was inspired by your GitHub repo (I had my eyes on it!) when I worked on it
I had lost the link to the spreadsheet though, thanks!
1/ I still don’t understand why we would want categories + subcategories! If the idea of categories/subcategories is just to have a dropdown menu in the UI with categories and subcategories, then yes that’s what I plan to do
But it’s just UI. The database is a representation of a model, putting 2 fields of type « category » « sub-category » here, would that bring anything? In terms of strict modeling, if we separate an attribute into two attributes, it’s because we want a subcategory to be able to belong to several categories. Not necessarily what we want, right? (open question, tell me if you have a counter example I’m interested!
).
2/ One of the values I put in the manifesto is that for Gladys 4 « we don’t do everything, but what we do we do well ».
In Gladys 3, I often wanted to go in all directions (to « be sure » to handle the case), there are categories that are useless, the types were open bar, we had « sentences » that were wired with nothing. In short: I had my eyes bigger than my stomach, and behind a lot of static data was wired with no code. And it was stupid because the user sees the sentence and says « cool I can handle XX », and in fact: no!
Here I have listed the « minimum base » of categories that I see. As we add modules (which will be in the core I remind you), we will gradually add categories. But as long as we have nothing, why put categories if we don’t know how to handle them? 
3/ What we said at the developer meetup was that:
DeviceFeature
- type: is used to determine in the UI which button to put. « binary » becomes an on/off button, « multilevel » a slider, « color » a color picker.
- category: Used for Gladys to know what « the object » is, and therefore to put an adequate representation in the UI at the icon level. Also used by the brain to fetch all devices of a category. « Turn on the living room lights », « What temperature is it in the bathroom? », « Is the garage door open? », « Lower the temperature in the kitchen », etc…
If you think of uses of subcategories (other than finding it organized for the dev, it’s a modeling there it’s pragmatic what we do!
), tell me, it’s indeed a subject that is better to settle now!
PS: but otherwise yes we can add the pressure sensor, anyway it will have to be added as soon as we add in Gladys 4 a module that needs to create one 