Yup. And besides Aloha, look at the hit parade of inter-island carriers over the years:
Mokulele (ERJ 170 operated by Shuttle America)
With all of the mainland flights that go to LIH/OGG/KOA, the need for lots of inter-island service is diminished.
You left out Discovery Air with their 146's.
If anyone could make an interisland op work I believe it would be WN.
I would argue anyone of the US3 or AS could make interisland Ops work as well or better than WN. For one, all 4 of the above airlines have exisiting brand recognition in the islands. UA has served Hawaii for 70 years as of this year and AS does a lot of advertising and sponsorship at/of local events.
The Interisland market is a lot different than Hawaii overseas flying. Brand recognition makes a difference to the residents living in Hawaii. As you note above, Hawaiians have seen a lot of airlines come and go and the impacts their departures have had. Having a long standing history serving the islands or being involved in local events goes a long way in this regard.
More than that, WN currently codeshares with no one. That means that passengers not coming to Hawaii on WN cannot connect to another island without buying a separate ticket. That means that WN would solely rely on O&D between each island. The higher density 737's they operate would be running between the islands without the added fill of connecting passengers. Almost every airline serving Hawaii codeshares with one of the interisland carriers. Unless WN changes their strategy i don't see it working well.
Additionally, AS+US3 have a wide variety of aircraft available to them to use which gives them the ability to right size capacity. Not every HA or WP flight is full. AS and the US3 would have the ability to serve off peak flights with smaller aircraft to better match capacity with demand.
The most important thing to note is that AS and the US3 do not operate Hawaii interisland for a reason. It's not as profitable as other routes they could use their aircraft on. History shows that the interisland market cannot support two or more large carriers indefinitely. The fare wars between AQ and HA almost put them under and that was before Go! came in. Go!'s entrance was the death blow at least to AQ. Not sure what magic WN would have that would magically allow the numbers to work for them but not AS or the US3. HA would defend their turf by lowering fares against WN. WN would likely leave the interisland market but not before doing damage to HA's bottom line. Sure the short term upside to interisland travelers would be cheap fares but at what cost long term?
In my opinion WP struggles because it cannot compete on schedule with HA on the trunk routes because it doesn't have enough planes. And because of its financial performance, is in no place to get more at this point. WP should have stay focused on the smaller markets like HNL/OGG-MKK, LNY and JHM instead of ceding those markets to HA with Ohana. MW seems to be doing alright because it's not trying to be something it's not, a direct competitor to HA.