Re: "We have now run out of IPv4 addresses"
If you are a new ISP then that is often the only option. In practice that means DS-Lite where people get a public IPv6 plus an IPv4 behind CGNAT. It can give you some annoying compatibility issues. I know a German ISP had a lot issues with people with Playstations behind DS-Lite.
For online services it might be more difficult. Would you put a range of externally facing servers behind CGNAT?