If you set an Epic on a Feature it should automatically inherit the initiative of the Epic. You could keep some flexibility if you want to allow customers to change the initiative afterwards, but I would be surprised if there was a feature that mapped to a different initiative from the Epic.
Mostly this comes into play when you go to the Initiative and then don't see a feature, you have to do double the work to tag each feature correctly.
You can now create an automation rule to copy the initiative of an epic to all its child features.