Changeable NAT-Settings, instead of deleting and recreating them.
It's just a small, but important improvement for admins who often change machine- and networksettings. would be great to have!
As a simple example:
New machine needs port 22 (SSH) to be NATed to its internal IP, so I can connect it from "outside", but also any other machine (maybe a test-server) might use it temporarly. the situation is, that I have to delete and recreate a new rule instead of simply changing its IP.