Dear kongondo
No problem at all. I'm not building anything yet, I don't know if I even could. I just had the same idea and found this post, so I wanted to ask what's going on.
I took a look at other builders like Elementor, js_composer, YooTheme and others. But to get something to work really well, it has to be a destinct solution for ProcessWire in the end. That takes a lot of time and skill, but it would bring ProcessWire to a lower threshold for users.
I think a builder would only make sense, if you finally could dynamically load fields and use selectors to get data for your builder elements like YooTheme is doing. I personally would do it for a commercial use, but I don't think it's viable.
Thanks