If going by ’tomohawk’s’ concept, the announcements are flexible, and better to record them as:
‘This is a Flinders St direct service, interconnecting to the Werribee line, stopping all stations’, to be announced from Frankston to Flinders St.
Then from Flinders St, ‘Limited Express Werribee service, running express Newport to Laverton’.
Another extreme concept is to rename the 20’ cycles to display ‘Bayside Line-Werribee’, and ‘Bayside Line-Frankston’, and advertise them to the public as ‘Bayside Flyers’. This way, customers can identify it as a definite Flinders St, Southern Cross thoroughfare. The destos can display two line messages as shown by the current ‘Not taking passengers’.
In the latter case, you would have ‘This is a Bayside Line service to Werribee via Flinders Street’. This is even more confusing than the first option.
I’m not too sure what the driver’s stance on checking the PIDs are, but many customers who have disabilities, and tourists rely on such information. The more information you display, the more people are likely to depend on this, and expect it to function 100%.