There were some NAT proposals, but I don't think any made it into the standard.
There is just no reason to use NAT if you have enough addresses. It's a hack to solve address scarcity, and doesn't add any security or any other benefits (unless you don't have a firewall, but you've got much bigger problems in that case!).
The RFCs for IP allocation say that every end site should get a /56 allocation - that is 256 subnets of /64 addresses [1]. A business site should be able to get a /48 (65,536 /64 networks) for no extra cost. Perhaps a mobile device with a cellular modem would get a /64 but that is the smallest allocation.
There is just no reason to use NAT if you have enough addresses. It's a hack to solve address scarcity, and doesn't add any security or any other benefits (unless you don't have a firewall, but you've got much bigger problems in that case!).
The RFCs for IP allocation say that every end site should get a /56 allocation - that is 256 subnets of /64 addresses [1]. A business site should be able to get a /48 (65,536 /64 networks) for no extra cost. Perhaps a mobile device with a cellular modem would get a /64 but that is the smallest allocation.
1. A /64 network has 2^64 addresses.