I think there are ways to implement dead-man controls with DCC, and perhaps even simulate vigilance controls such as what RailCorp has fitted to all our Sydney suburban trains in the blind belief that it solves all the problems of trains going out of control when a driver becomes incapacitated... 8-)
I don't think the hardware side would be too tricky - it just comes down to designing and positioning of appropriate switches and actuators for them.
The software side might be a bit trickier since there needs to be a way to first of all interface a pushbutton of some sort then a way to integrate that with the command station firmware to shut down a train if the button is released when the train's 'master controller' is not in the 'off' position.
Vigilance would be similar, and be a lot more of a software approach since it involves timers, etc.
DCC throttles could easily be designed with one or two extra buttons - one for a deadman feature that needs to be held in at all times otherwise the train being controlled will stop, and the other for vigilance when needs to pressed within a predetermined time period or the train will be stopped.
The deadman switch would need to be something easy to depress but set up in such a way that the simple action of releasing the handgrip around a handheld throttle drops out the switch. the VC switch can be a small pushbutton somewhere.
Regards,
Craig.