Damaging the metro side of the service to slightly speed up the cross country side feels like a bad idea. When I lived in this area I found the closely spaced stations very useful. If there was an opportunity for the long distance train to overtake it would allow both services to improve.
The biggest recent improvement to train services in West Sussex is the June 2024 West Coastway timetable which was implemented with no change to the infrastructure.
The following six train services an hour each way which provide the Monday to Saturday train service since June 2024 for the 13 stations Angmering to Hove inclusive are really all metro services:
2tph Littlehampton to London Victoria serving the following 9 stations: Angmering, Goring-by-Sea, Durrington-on-Sea, West Worthing, Worthing, Lancing, Shoreham-by-Sea, Portslade, Hove
2tph Southampton Central to Brighton serving the following 7 stations: Angmering, Worthing, Lancing, Shoreham-by-Sea, Southwick, Portslade, Hove
1tph Portsmouth and Southsea to Brighton serving the following 11 stations: Angmering, Goring-by-Sea, Durrington-on-Sea, West Worthing, Worthing, East Worthing, Lancing, Shoreham-by-Sea, Southwick, Portslade, Hove
1tph Chichester to Brighton serving all 13 stations: Angmering, Goring-by-Sea, Durrington-on-Sea, West Worthing, Worthing, East Worthing, Lancing, Shoreham-by-Sea, Southwick, Fishersgate, Portslade, Aldrington, Hove
Only the hourly all stops Chichester to Brighton train calls at Fishersgate and Aldrington. GTR dropped them from the hourly Portsmouth and Southsea to Brighton service to provide attractive journey times between Portsmouth and Brighton. All trains call at the 6 stations Angmering, Worthing, Lancing, Shoreham-by-Sea, Portslade and Hove.