Several people have pointed out that increasing numbers of cruise ships are calling at Invergordon and Scrabster nowadays, and they have wondered whether trips by train could be provided for those passengers wishing to spend time ashore. At present there are several trips by coach laid on at Invergordon - the position at Scrabster is not known as there are far fewer ships calling there. It is common in the cruise industry for passengers to pay, sometimes quite a lot of money, for these "extras", so expense ought not to be too big a problem.
Such shore-based excursions are organised by a small number of agents, mostly based in London, who operate internationally. The cruise operator has little or no input, and merely gets a percentage of the price paid by the passenger. Margins are very tight, and there is no scope for speculative provision of a new type of tour. Almost all are coach-based, and most are well-established, having run - and proved to be financially profitable - for many years.
Breaking into this market, especially with a new product (like a train trip), however attractive and different, is well-nigh impossible. In order to succeed with an agent a third party would have to guarantee a level of income in the first year (at least) even to get an agent's serious attention.
The operational logistics of providing a dedicated special train on the FNL would be substantial. Using the scheduled services would be unwise until a significantly greater degree of confidence in the accurate delivery of the timetable could be assured.
In short, while this looks good on paper, it is wholly outwith the realms of reality.