HEX was only convenient if staying at Paddington, i never thought it worth the premium over taking Picadilly line, given the back tracking needed to get to a convenient station. Elizabeth line priced in between but then only useful for some parts of the city.
Re trains to SYD if you sit in vestibule area not really any different to picadilly line trains which dont have a dedicated luggage area either. Noting NYC trains from JFK and NJ Transit (2 story like Sydney trains) which you have to take from to NY from EWR also no dedicated luggage area, not a deal breaker.
Of course WSI wont have special trains to city or anywhere else either, have to get on same style Sydney Trains as service SYD from St Mary's just travel for much longer.