Farci: yes, there are non high speed corridors in Spain where upgrading and even new construction is likely to be good value for money.
But for me it is desperately sad that effort is spent on routes that will never happen and that people's hopes are falsely raised when, if you explain to them the basics of demand (current and possibly generated) versus cost, it is clear effort is better spent elsewhere. A part of my working life was evaluating infrastructure projects so I can look back at 40-50 years of success and failure. Much of what Spain has built since 1986, motorways, high speed rail and urban transport really has added value to the economy although with over-enthusiasm e.g. in the empty spaces, as you know, diverting investment that would have been better spent elsewhere.
So on the conventional network upgrading Zaragoza-Teruel-Valencia to increase freight capacity and reduce journey times is valuable. Similarly Algeciras-Bobadilla and most of the Mediterranean Corridor. By contrast, the idea of Sines-Badajoz-rest of europe, despite its early TEN-T status, was always a triumph of politics over reason.
The people of Seville will get more direct benefit by pressurising MITMA (=DfT), ADIF (=NR) and the region to accelerate work that is already planned with sustained investment (yes, it seems better than it used to be, from outside at least) and not get distracted. Look at how long Cadiz tram took. How long was Antequera without a functioning station, let alone the rest of the route? Why was Huelva-Zafra modernisation started instead of increasing effort on Algeciras, and so on. And please, please divert any Huesca-Canfranc money somewhere more than a few thousand people will actually benefit!
End of rant.