In every bank I have worked for we used the time delays. The working supply was kept to a minimum. This also helps in your dual control / sole control measures. Your time delay can be kept under dual control and your working supply can be kept under sole control. This helps when you transfer your vaults.
You can also implement a timer on the teller stations if you are going to permit them to maintain more than a "normal" teller working supply. this would be used for making change for businesses, etc.
I think to safeguard the employees the most important thing is training. You can never train them too much. Don't allow them to take it lightly. It may save their life sometime. Prepare them so if it happens, they won't melt. It will be automatic.
Opinions are mine not my employer.