Does the WLIP support incoming connections for any type of web service? If not, IMHO you don't need to do a thing. Many ports are designated or "well known" for specific types of connections, like http=80, ftp=21, and such. If you had a webserver of some sort, then you might want to route xxx.xxx.xxx.xxx:9999 (isp assigned IP:random-port) to 192.168.xxx.xxx:80 to hit it from outside. (It's a cheap security trick to change the inbound port of security cameras with built-in webservers to something other than the default of 80 or whatever, to make it harder to find by chance) Otherwise, I personally don't know what benefit it would bring.
I WOULD however reserve an IP address (whatever it has now), assigned to the MAC address of the WLIP in your router's DHCP table. That was it is always assigned the same IP address whenever it registers. That just makes it easier to keep track of, after power resets of your network when you want to access it from behind your router (LAN).