This week seen very little progress, as I'm stuck in personal problems, like a minor car crash...

That being said, let's move on.

It's amazing how silly things you ignored/disdained for a long, long time suddenly shows up and you perceive how incredibly useful they are! It's pretty like a Eureka moment.
Yes, I'm talking about you, Pull Up/Down resistors. These guys, in conjunction with 3-state buffers, are all you need to make bus-driven circuits.