I have seen the proposed changes timetable, and there isnlt much there to 'improve' the service. There are a few things would immediately improve the service (at least from an Arun Valley perspective) however.
A later departure from VIC along the Arun valley (the current 22:30ish departure is not much use). People want to use the trains, but if the service isn't there (theatre, concerts etc, normally don't finish in time to get to VIC for the last train of the day), they're not much use. People drive to Horsham or even across to Haslemere to get the later services (good I suppose for car park revenues).
The proposed timetable changes make the Portsmouth service much slower, so renders the splits at Horsham rather pointless. There was a lot of anger when Southern introduced this from passengers along the Arun Valley, removing the direct Chichester service from the Arun Valley stations, as well as making the journey to London longer as there is an additional wait at Horsham for the 'fast' section to arrive/depart. It would be better for the passenger to return the Bognor split back to Barnham. Naïve I know, but the degradation in service was not reflected in the ticket prices from our local station...
Reinstate the well patronised London Bridge directs. The justification for their withdrawal was straight out of the Beaching sleight of hand play-book. Withdraw the later afternoon service and then say the service isn't used. Guess what, the 18:05 was withdrawn 'due to Covid' and the 17:05 was retained. A 17:05 departure from London Bridge may work for Southern managers and Civil Servants, but was pretty useless for those who actually do a day's work in the city. The trains to London Bridge are now very well patronised, with large numbers of passengers joining the Thameslink services to get to the city. There is certainly a case to reinstate this, and other LBG directs.
I know Southern have no intention of doing any of these things - they spent years trying to dump the London Bridge directs, so I don't expect them to return, and given the rather pathetic excuses given not to run a later train (engineering works was one (do they have engineering works every night on the Arun Valley? Of course they don't...)), that ain't going to happen either.