It gets quite annoying when I wait at a station to take over control of a service only o be delayed by having to unlock the master key, set the reverser turn on safety alarms e.g AWS and release brakes it usually means I'm late for the next stop. I know technically trains are always late anyway in real life but I actually try to be on time in the game on GWR which is more than can be said for real GWR/FGW drivers.
When a driver swaps into a service, usually the outgoing driver will remove the master key and secure the train with a full service application and move the reverser to neutral/off. (At least in the UK) The incoming driver inserts the key and re-prepares the train as passengers board. It's why some services in real life have longer dwell times as crew changes etc. happen. Agreed that you shouldn't have to enable AWS/TPWS/DSD though, they should be on anyway :P It's a problem with Rapid Transit especially for me as often I need to fully reset the train before I set off and then I'm late. A simplified restart procedure would be a welcome suggestion though!