Hi,
To be honest I have never had to resort to ever trying such a NAT configuration on the software level you are using.
Though to my understanding its possible in the newer software 8.3 and newer with the new NAT configuration format
There the configuration could look something like this
object network STATIC-PAT-1
host 10.0.0.123
nat (LAN,WAN) static interface service tcp www www
object network STATIC-PAT-2
host 10.0.0.123
nat (LAN,WAN) static 1.1.1.2 service tcp www www
Both NAT rules seemed to work fine with regards to testing them with "packet-tracer" command.
Seems the behaviour is a bit different on different devices.
I for example tested the configuration format you used in a Cisco FWSM which accepted and entered both "static" commands even though giving the warning. An ASA 5510 running 8.2(2) on the other hand gave the warning and rejected the second command.
- Jouni