> For fully autonomous operation you need extra security features on the track which were not employed (fully sealed off track in stations, better emergency corridors, more reliable remote door controls etc.).

FWIW Lyon's Line D is fully automated (GOA4) and doesn't use enclosed track. It may have changed since but it used to not even have turnstiles, you could walk up to the track without any pause.

The only incident I can remember is a drunk who literally fell on a train from one of the elevated passages over the track.