I guess the northernmost and southernmost half an hours would be viable commuter services. However, at the southern end I’ve always thought (Southampton -) Bournemouth - Templecombe - Yeovil - Taunton (- Exeter etc) would open up a whole host of interesting journey opportunities, some of which aren’t there on the current network. I think i may have said this before here.
However, in truth, it’s difficult to imagine it would be much busier than Yeovil - Weymouth for the most part, which has never seemed to be busy enough to deserve any kind of properly regular service. The real problem with the S&D is there wasn’t a decent size town on it for the most part.