You can mimic the NAT'd functionality from Lab Manager by creating a vApp Internal Network and then connecting it to your External network within the Organization. If you have an IP Pool configured for this network and choose this selection on your VM's within your vApp it'll function just like Lab Manager did.
You should also be able to do it with vApp networks, which is the close equivilent to Lab Manager "Virtual Networks". When you create a vApp network, you can assign an network to NAT onto. This is basically your "Connect Virtual to Physical" feature. This is just in case you used Virtual Networks and the Connect feature, verses Physical Networks and Fencing. The two features were virtually identical, but just had different names.
The drawback to this is if the config is cloned the IP addresses go with it. You will only be able to start one vApp at a time unless you change the networking on the cloned vApp. We do this for some long-term testing/development vApps where we have to create other network ACL's in order to connect to it.
If you directly clone a vApp with the "Retain External IP Addresses", the source system should retain the setting ... the destination system should not. I haven't tested this, but would make sense to me.
If both systems have the Retain External IP setting, you'll have to disable this before powering it on again so that the new NAT IPs are assigned. Then you can re-enable the feature to "lock in" the newly assigned IP addresses.