In this photo you can see the overall plan for the Harbour and Beach Park. Two things will strike you from the overhead photo of the model: firstly, that a large area of land (the former Ayrshire Metal Products/Dockyard site) was proposed to be flooded in order to create a marina, you can see two illustrations of how this may have looked on the right of the photo); and secondly, almost two-thirds of the current Beach Park was to be developed for housing and a hotel (you really have to admire Irvine Bay for coming up with a near-identical solution, perhaps their consultants did spend some time in Irvine after all, looking up the 1971 Plan in the Library).
In terms of the marina proposal, I think that the flooding of such a large area of land would require a lot of detailed investigation. Of particular concern would be how this might affect the harbour and the wetlands between the Rivers Irvine and Garnock. It must be remembered that our knowledge of the ecology of water habitats was much less sophisticated 40+ years ago. As for the Beach Park, there's not a lot of it, is there? Such a large development next to the shore would do irreparable damage to the fragile sand dunes and ruin the feeling of 'getting away from it all', which you can get on the beach. Another thing is, how much traffic would all this generate, the roads on the model are pretty wee, could they have coped? The model also shows the western end of the 'superstructure' which was planned to start at the Cross. This was to comprise of a college, council offices and housing, all served by a monorail. You've got to love them, they had obviously spent too many hours watching Stingray and Thunderbirds!
This photo was taken by George McMaster, around 1971/2. If you look to the left of the image you can make out the barrier for the Marress Roundabout; to the right, and through the trees of the Low Green, you can see that the westernmost part of Bridgegate is still intact.