I don't think I would recommend that especially to a newer shooter. It forces you to put your finger on the trigger to release the safety?!! That doesn't sound like it makes anything safer.. if you need an external safety then a glock is not for you. This is creating a problem where there isn't one..
You do not have to put your finger "on" the trigger as in pulling the trigger. Only on the side to push the button left to take safety off.