The document you created is a perfect starting point. Thank you for taking your time to do that. And definitely a must, to keep the whole idea organised.
But instead of directly commenting there, I think it would be better to open separate topics here on the forum, to allow discussions here and then come up with a conclusion, which then will be reflected on the document.
Using the document as a discussion platform will be a bit messy, and also it will be better if the document only contains specifc and clear descriptions. If there are too many words it will be harder to understand. Less words, clear decisions. Decisions that will have previously been discussed here on the forums, to keep track of all the “WHY THIS?”
I also propose adding a Use Cases section, to start by the most fundamental thing: what real problems are we trying to solve with this?
Knowing the real needs we can create a solution that is designed to solve those needs. Maybe some type of relationships are never used, maybe there is some side case that has not been considered, etc…
So I will open a topic specifcally for that. Here it is. And I think we should open specific topics for each discussion-topic: Single Pattern vs Alternative, API design, UI design, and so on. Of course, not open them all at once, it’s preferable to approach this step by step.
We can keep this topic and the Google Doc as an index.