Who manufactures DHC7 aircraft in this day and age, where is the additional ISC fire cover to come from and, were a runway extension feasible, who's going to finance it ... ISC can make comparisons to Scotland blah blah blah but in Scotland they're still operating Twotters on a sand beach but only when the tide is out.
The Scillonian (vomit comet) ferry is past it's sell by date, the Twotters are getting towards their sell by dates, PZE heliport is closing and the choppers will struggle to compete vs fixed wing on a NQY/ISC/NQY route, they might only survive on a Tresco route where no fixed wing can compete ..... So why not do away with this mixed bag of geriatric equipment and invest in some modern aircraft, namely hovercraft, equipment?