This is a really good idea. That said, depaving is not easy. Anything paved will have compaction issues and lack any sort of organic matter. On top of that you need to check for contaminants.
The crux of getting the movement going is this:
Without planning and private land owner buy in it's hard to get rolling.
E: someone ask me how I would go about this all - fair warning I'm a mega nerd on this stuff