when ever a change to config is made, create a a backup of the previous config
when ever a change to config is made, create a a backup of the previous config with an option for auto rollback. this is useful incase a config change locks out the administrator. other vendors such as juniper already include this.
This is a really important feature that would greatly improve the resiliency of the system along with helping protect users from themselves.
Expanding on the original idea a bit - let's extend the backup library beyond just the most previous. For example, with pfSense, configs are saved on a per save event basis and all configs are time\date stamped along with an overview of what changes were saved. In essence, each of these backed-up configs is a restore-point that can be used to take the system back to a known good condition at some point in the past.
Additional add-ons to this would be to specify how many configs to keep -both on a discrete number and date basis; how long to keep configs; ability to specify individual backups as persistent so they are not purged or deleted unless explicitly done so by the user; specify a backup config as the auto restore point; etc...lots of great things become possible by implementing this feature.