> We are considering using other unused address ranges, including the otherwise wasted 0.x.x.x

0.x.x.x is currently incompatible with WordPress: https://github.com/WordPress/WordPress/blob/641c632b0c9fde4e...

To put it another way, 0.x.x.x and 100.x.x.x don't have equivalent properties in WordPress. 0.x.x.x is blocked in some cases to prevent SSRF attacks. 100.x.x.x is considered a "normal" IP address.