With the impending event of the source code becoming open source, I've started work on the design document for the game. I will be as detailed as possible, so hopefully this will answer most of your questions on how a feature should be added.
If you spot a potential issue or improvement, feel free to let me know! If the document is not clear enough, go ahead and ask questions. The goal is that you can help me complete this game.
So far, I only have two pages (I just started today). But I foresee it going up to 50 or so pages easily. There'll be a lot of details to cover. I think in a way, it will help me avoid feature creep if I establish the boundaries in the design doc :)
Here's the link to the document:
Beyond Beyaan Design Document