However most of us live with dynamic prefixes, and this becomes a problem..luckily one way around this is to use ULA addressing internally, and map those addresses in DNS.

Then combine that with DynDNS or nsupdate if you are using your own domain name for the WAN side and configure port forwarding or a reverse proxy. You could also probably use NPTv6 to deal with dynamic prefix mapping but that's another beast all together..