In addition to the extra train that would have been required in 1967, if Ventnor had remained open, as previously mentioned in this thread, it is my understanding that a further sub station would have also been required, and I assume that would have been a significant proportion of the budgeted £80k mentioned.
As also previously mentioned the estimated journey time of 38 minutes or so is not a particularly convenient timing. If the railway to Ventnor was open today and presumably a half hourly regular interval frequency was to be maintained, at least four extra Cl 484 units would be required. I assume in that case the trains would pass at Sandown.
I note the inconvenient location of the former main Ventnor station, and arguably the other Island stations are not in the most convenient locations either. Sandown being quite poor in this respect, but the secondary school is nearby, which together with residents local to the railway station, must be useful income generators for the railway. The key useful aspect of the Island line is it's convenient and relatively quick connections with the mainland via the Wightlink ferry with step free access, unlike the Hovercraft service at Ryde, which visitors from the mainland appreciate. These aspects offset the relatively poorer access issues to the centre of the main places served by the railway on the Island. With the closure of Ventnor station in 1966 did result in a significant turndown in business for the town, and in today speak is probably one of those left behind places. I am sure if the railway was reopened to Ventnor the town would gain extra business, but the key 64 dollar question is whether the significant cost is justified.