To use your example on: Alternative to Port 80 for http
Configure *.example.com to IP 188.8.131.52 port 80, portforward from publicip1 port 80 to port 80 on your server, point dns for example.com to publicip1
Configure *.domain2.com to 184.108.40.206 port 81, portforward from publicip2 port80 to port 81 on your server, point dns for domain2.com to publicip2
Repeat increasing the the local port for each website that you want.
Note: If you ask for additional IP's using this as your justification you will be denied, as this is not a valid reason for additional IP's.
Your private network in Go Daddy Cloud Server Console is private to you, you can add as many private IP's that you want to your servers. Only those in your subnet will be able to get out to the internet (NAT'd behind the primary ip). However, we currently only support configuring port forwarding rules to the internal IPaddress that was assigned to the machine. IE you can add whatever IP that you want, but currently we will only use the original private IP address to assign rules.