I haven't been to Porthcawl for a couple of years, so I'm a bit out of date with current developments there, but a modern single track line with occasional double track sections doesn't take up as much room as a road, so I'm sure that some route could be found. Though it's the expense of such land purchase that would be the biggest obstacle as I doubt anything remains in public ownership.
I think your concerns are very valid, and I have similar thoughts. It would, though, help the town to attract more visitors in, while helping the residents gain access to Cardiff and Swansea.
The provision of some sort of rail link itself would make the area more attractive to residents - one could be in Cardiff or Swansea in under an hour.
While Maesteg may have a greater population in its catchment area, a railway would stimulate population growth, and Porthcawl is probably more attractive as a destination for visitors than Maesteg (no offence to the latter).
Having said that, there are lots of other schemes that appear to be far more viable and deserving of funding, so much as I would like to see it happen and think it would be beneficial to the area, I doubt that it will.