Then the guards door (rear cab) would need to be on the platform for them to get out and go open the local door with the egress.
Yup, quite agree. A simple stop marker in a suitable location, and a local instruction on the above method of working. Customer friendly rather than just 'sorry, this train can't stop there' - I'm not advocating it becoming normal operating procedure, but just in exceptional circumstances when a 3-car finds itself on a 2-car Turbo diagram.