I would like to see a Somerset, Wiltshire, and Gloucestershire Taktplan with clock face departures as follows:
Local services
Bristol Temple Meads - Severn Beach every 60 minutes
Bristol TM - Bristol Parkway via Henbury every 60 minutes
Gloucester - Weston-super-Mare via Filton Abbey Wood every 30 minutes, calling all stations, plus extensions every 60 minutes to Taunton
Bristol TM - Portishead every 60 minutes to start with, possible increase to every 30 minutes if popular (link with Severn Beach/Parkway above?)
Bristol TM - Bath Spa shuttle every 30 minutes (calling all stations) just after the London Paddington via Chippenham trains have departed, and before the ex Cardiff - Portsmouth arrives at Bristol TM
Bristol TM - Frome every 60 minutes calling all stations, with 2 hourly extensions to Weymouth via Yeovil Pen Mill
Swindon - Salisbury via Melksham every 60 minutes, calling all stations, plus the proposed re-opened near Salisbury (unsure of the name)
Bristol Parkway - Westbury every 60 minutes calling Filton Abbey Wood, Keynsham, Oldfield Park, Bath Spa, Freshfield, Avoncliffe Halt, Bradford-on-Avon, Trowbridge, and Westbury
Regional limited stop services
Cardiff Central - Bristol TM every 30 minutes calling at Newport (Gwent), Severn Tunnel Junction, [Pilning]*, Patchway, Filton Abbey Wood, and Bristol TM (*limited calls until new residential developments are built, if ever. Every 2 hours to start off, then build the frequency from there afterwards). Note that this is more of a shuttle service.
Cardiff Central - Portsmouth Harbour every 60 minutes calling Newport (Gwent), Filton Abbey Wood, Bath Spa, Bradford-on-Avon, Trowbridge, Westbury, Salisbury, Romsey, Southampton Central, Fareham, Cobham, Fratton, Portsmouth & Southsea, and Portsmouth Harbour
Bristol TM - Portsmouth Harbour every 60 minutes calling Bath Spa, then as per ex Cardiff - Portsmouth (could run non-stop between Bath Spa and Westbury and couple to the ex Cardiff portion there)
Bristol TM - Great Malvern every 60 minutes calling Filton Abbey Wood, Gloucester, Cheltenham Spa, Ashchurch for Tewkesbury, Worcester Shrub Hill, Worcester Foregate Street, Malvern Link, and Great Malvern
Note that the above are just my thoughts and fantasies, and I have not yet laid it out in a spreadsheet to see how it would all look like. I have switched the present Cardiff - Portsmouth to run direct between Filton Abbey Wood and Bath Spa so as to help provide timetable robustness, but have compensated for a twice hourly Cardiff - Bristol TM shuttle and a Bristol TM - Westbury - Portsmouth (which could be coupled to the ex Cardiff at Westbury). I have split the present Cardiff - Taunton via Weston-super-Mare, so as to keep things simple all round for a Taunton - Gloucester via Weston-super-Mare all stations service.