The main thing that needs to be done, urgently, is to clarify for marshals that, if they do what they have been trained to do, as they have been instructed, and do not do something like shortcuts or breaking rules (laws) etc, they are NOT going to be held responsible for something which happens.
You can only be held responsible for irresponsible actions. This needs to be officially reiterated at a high level.
There also needs to be some way of telling them they are protected by the powers that be, in terms of defence if they are accused, and of damages if something happens to them.