Allow auto-accept :
defaults write com.apple.FaceTime AutoAcceptInvites -bool YES
Auto-accept FaceTime calls from a specified email:
defaults write com.apple.FaceTime AutoAcceptInvitesFrom -array-add email@address.com
Auto-accept FaceTime calls from a specified phone number:
defaults write com.apple.FaceTime AutoAcceptInvitesFrom -array-add +14085551212