Being able to close and open the vault door. I don't know if it is easy but my thoughts are to either reverse the animation or use a switch state script in the GECK when it is released. I think it would be useful when creating Vault player homes or safe storage. That was the only feature that I wish FO4 had. It may increase immersion and help with roleplay. for example: you seal yourself back into the vault after the events have unfolded.