I have only used the Far North Line once, and that was in the Autumn of 2021, I had to visit a facility in Bower and Georgemas Junc was the nearest station. I was met at the station, as was the only other passenger getting off, no one got on... The return journey was by air from Wick, but on the outward journey flying didnt work. The train was not busy, and a lot of the passengers who joined at the start in Inverness seemed to be headed for Thurso. Really the Kyle line is a better scenic route from Inverness, the flow country is worth seeing, but if I was planning a day trip from Inverness I would go for Kyle.
Saving minutes on a 3 1/2 hour journey isn't going to increase passenger numbers. To appeal to tourists you need decent rolling stock, and for people like myself travelling from much further south connections at Inverness are the thing. Even with A9 improvements its worth noting that the driving time from my neck of the woods is around 10 hours, and that is going to be tiring, and flights are even more infrequent than the train.
My own view is its probably best left pretty much as is, but given the infrequent service reliability has to be the most important thing.