Would that mean, for example, that Skybus is burning money on its Islander-operated LEQ-ISC route which at 31mi is pretty much like ACI-GCI (26mi)?
IMHO, no aircraft per se can be deemed "uneconomical" no matter what. Economics are defined by what income you can generate with the aircraft. So the question is how much an airline could charge. Fares would need to go up, of course, but I don't see why it would be the end of the world without the Tris. All over the world islands are connected with 8-19 seaters that are not Trislanders.