A+P is for home gateways, not for servers. That said, most uses of A+P
exclude the well-known port range for assignment to home gateways, so if for
some strange reason you wanted to do A+P with servers, you could allocate those
ranges to servers. This is not a common or expected use of A+P, however, so
this is kind of moot. The essential point of A+P is that it creates
deterministic mappings, which makes carrier-grade NAT less painful and more
predictable. It really only makes sense in the context of a dual-stack
transition model, where you would always prefer IPv6 for flows between hosts
that support it.