I suspect you are right about Malaga Centro - Alameda station. Like in the UK, cost cutting seems to really damage any future proofing of many projects in Spain. The line to the Port has been disused for quite some time now and the street level track that runs down to the port is very overgrown currently.
Yes, it was really shortsighted, especially when you consider how profitable the Malaga-Fuengirola line is. I suppose the major issue was the infrastructure needed, especially the viaduct in Fuengirola and the cost of providing double track tunnels. Still, I don't understand why they didn't take the chance to extend the double track tunnel into Malaga Centro - Alameda when it was closed for refurbishment, as it only needed around 500m of tunnel and a larger station space.
Thank you for the information about the Port line. I've only ever caught glimpses of it when in Malaga, so I didn't know about the general state of repair of the line.
I like the idea of 4 tracking a new cercanías station at Plaza de Marina. I can't see it happening in my lifetime though.
Malaga seems to be pressing ahead with the new bus station plan there, so perhaps it's not entirely impossible that they'd build a new terminal station there. But it all goes back to the problems of the line itself, in that double tracking it isn't going to happen without a huge amount of protest and problems. Perhaps one solution could be to consider building the new terminal station at Plaza de Marina, then expanding the station in Torremolinos to include two terminal platforms along with double tracking the route between the airport and Torremolinos? This wouldn't be too difficult to achieve, as there's plenty of space for a second track along that section.
Several projects have been made for C-1 extensions east or west, but the costs are really high.
The cost of building the C-1 west would be astronomical, although it would really help if places like La Cala de Mijas and Calahonda had stations. The A-7 is really struggling to cope with the amount of traffic now, especially the Fuengirola bypass.