Your Portsmouth path would be fine if you moved departure forward three minutes to xx08 from PMH, then xx12 PMS, xx16 FTN, xx24 CSA, xx32 FRM, xx56 SOU.
The Chandler's Ford path is interesting, however, it does mean the FGW trains leave SOU 10 minutes apart, rather than the more respectable 25 minutes apart on my plan. Also, you'd have to be prepared to axe the CFR/ESL/SOA calls if anything is running late! However, mine does count on either a slight retiming to the Romsey - Salisbury service (moved back by a few minutes), or a modification of that service to run Salisbury - Lymington, which would still provide 3tph from Southampton to Salisbury; 2 direct and 1 via Eastleigh.
I have also made some changes, briefly:
WEY - BRI extended to BPW, calling all stations.
PMH - CDF only calls at FIT on hours when the above doesn't run.
WAT - BRI path moved to fill in a gap in the BTH - BRI service. Ideally departures would be from SAL at 0752, 0952, 1152, 1552, 1752, 2052; giving Bradford-on-Avon and Keynsham a near enough 2tph frequency.