It clearly hasn't occurred to you that private collections evaporate over time, just like public ones.
> I would like something that not only archives pages I visit, but also versions them and tracks changes.
That's a huge storage requirement, you must realize this. If you're an avid Web browser, and if every archived page had to look as it originally looked (i.e. all the linked resources) you could accumulate several terabytes per week.
> This type of system would be a huge boost to something like the wayback machine.
Here's the road to madness. Someone, aware of the rapidly declining cost of storage, rebuilds the Wayback machine based on your scheme, with the intent of archiving every Web page in existence, including all required resources so the pages look just as they originally did. Then, as the project approaches completion, this genius says, "For the next phase, I need to archive the Wayback machine itself." At that point, as the implications of what he's said occur to him, a strange look crosses his face and his imagination begins writing checks his intellect can't cash.