Surely the point of introducing larger aircraft would be to enable flights to other destinations, rather than simply to replace the helicopter and sky bus flights? With a dhc8 100 you could add connections to London and Manchester (perhaps with a tech stop at NQY outbound from ISC). Or is this the problem, that the islanders don't want to more connected to the outside world?
If a dhc8 operation was established, there are plenty of qualified crews in the south west.....