The reductions were nothing to do with ORCATS▸ anyway, they were removed on request from the DfT» about service duplication. There was no need for it & saved both units & staff time if removed. As the DfT is still looking to shave the budget, there is no chance of the duplications being reinstated IMHO▸
Another take: the service met a whole slew of different travel needs for people, was popular and well used, and as long as the railway doesn't introduce and develop this sort of service as part of addressing the glaring shortcomings of rail travel in the south west arising from the shortage of staff, rolling stock and infrastructure, it's relegating itself to a legacy transport mode.
Mark
There are different cases here and each of them may have a different best outcome
* I have watched with interest how south coast services from west of Southampton, which head up to(wards) London have or have not headed out along the south coast along to(wards) Brighton and remember discussions about some of the smaller and sparser served stations did or could have lost London service. If you can only justify one train per hour (and I don't know it enough to say if that's reasonable) then where and how far it should it go beyond Southampton is an interesting question. Or ... do you "flipflop' at Southampton when the stopper from the West alternates between carrying on via Fareham and via Winchester - every line / station served hourly but alternating which start / terminate Southampton and which go through.
* Bristol - Salisbury and Salisbury - London stoppers both use 15x trains and it is, frankly, hard to justify that six years ago a number of these were through trains and now they are disjoint and to the detriment of customer service.
* Reading to Salisbury; I don't know. Start with a look at traffic levels between Basingstoke and Salisbury, and a look at the traffic levels across Basingstoke.