I wouldn't call a 8-10 seater chopper increasing capacity significantly in lieu of a Twotter, Twotters are in production again and I'm sure there are a few available on the market somewhere.
The LEQ chopper has to be destined for a Tresco route, I can't believe that it would be for St. Mary's.
The talk of PZE vs LEQ weather when the biggest problem is ISC fog, the minima is/was an RVR of 1500m which is pretty much impossible on a 600m runway, fog clears by the sun heating up the land and lifting the fog but in ISC there is so little land the approaches remain clagged up, in such conditions the choppers were more successful at getting in than the Twotters, they could simply go in to the overhead and drop in!
One concern I would have is that the proposed LEQ chopper is from a Gloucester based operator, ISC has it's own somewhat unique weather problems, Brymon had some 'special' Captains that knew the place like the back of their hand, one Captain 'Doc', all he had to do was sight his rock that he used as a navigational aid and he could get in, I believe they still refer to it as 'Doc's rock'
But the S61 that went in was crewed by an ABZ based crew, apparently they became disorientated and the rest is history, it should take local pilots with a local knowledge in such conditions.