That sounds more achievable. However
a rail interchange constructable for less than £250K
does not. No new rail station ever comes that cheap. And if the sole purpose is to attract traffic which currently uses BFS and BHD I don't see the point, even if you could attract them with a two-hour plus journey from Belfast followed by 300 metres of lugging your cases along a windswept walkway. In any case airport managements hate rail links because they make no money out of them.
NS