I think this sounds great. I was searching for exactly this kind of software, when I saw this thread. It might be that non-visual people don't need this, but I really miss it, 'cause I want to se better how tasks and projects are related to others.
I think it's strange that nobody hasn't done this before. I would love to se an app where i can make a flowchart for a project, and then switch to a task view, to start doing things.
SmartDraw is doing something like this, but only with a mind map. I think a Flow chart is more precise, and depenencies are a very typical issue in a project.
Would love to hear more about how far you have come with your project.