Comment by eqvinox

That's all true on a statement level, but doesn't make an IPv4:IPv4 NAT solution better than either VRF/encap or IPv6 mapping.

The benefit with VRF/encap is that the IPv4 packets are unmodified.

The benefit with IPv6 mapping is that you don't need to manage IPv4:IPv4 tables and have a clear boundary of concerns & zoning.

In both cases you don't give a rat's ass which prefixes the customer uses. That math/estimation you're doing there… just entirely not needed.