Have seen plenty of reference to LCY on this thread. Having prepared a flight feasibility study for a route to LCY using F70 with a 120 min stage length, I can see many parallels on why a commercial service to SHA will NOT work given the current setup:
At LCY we found (much to our initial surprise) that the primary limiting factor was not LDA, but TORA. Given the availability of suitable alternates, landing weights would have been low even with a full commercial load, permitting safe ops even on wet runway conditions. Using Met Office data, we estimated that on a year-round basis less than 2% of the flights would have required a weather diversion to STN, that is one flight every two months on a daily service, well within acceptable limits. However given the required trip fuel, to meet one engine out performance, wet-runway takeoff was only possible with a 50% reduction in commercial load - and data indicated wet runway conditions likely for 180 out of the 365 days of the year. This effectively killed the project, as technically it would have been possible, but commercially not viable.
The same applies to SHA. With the diversion alternates all 2-3 hours away, there will be little difference in landing and take-off weights, the alternate fuel being the trip fuel for the return leg. Wet runway conditions will have a severe impact on permissible payload both in and out, the wind condition only has the effect of reducing LDA. With reduced payloads seat cost will go up dramatically, well beyond the levels acceptable for unsubsidized tourist traffic. Of course SHG may chose to give subsidies to residents and public service traffic, but that will mean low frequencies/small aircraft, hardly the promised tourism boom that was the underlying business case for the whole airport.