Yeah, it's completely nuts to limit STR in Chelan. It's so small and this is basically what the economy is based on - tourism. I lived in WA for nearly 20 years, from the White Salmon area to Seattle, Bellingham - I owned a house in Sumas on the Canadian border, too.
You know what might work for Chelan for the workers who need to live there year round, is to find a LIHTC (low income housing tax credit) investor group to build an apartment complex or two in town. I lived in Crescent City, CA, which has a population of around 5,000 next to the giant redwoods - it's a tourism town, and I lived in a LIHTC property there. There are several in town.
Sometimes they build brand new apartment complexes and sometimes they purchase (with subsidies from city/county/state and feds) old hotels in downtown areas to revitalize an area. They'll be mixed use, usually, with shops on street level and apartments above. Sometimes they're family and sometimes 55+ or older seniors/disabled. The landlords get full market rent, but the renters pay a lower rent and the landlords get subsidies for the difference. They're really profitable for the investors and supply a low income housing supply for a town.
Maybe you could look into this and find an interested investor group to present an investment project in town.
Also, presenting numbers can be persuasive, as far as the city council goes. Show numbers as to how much revenue they're losing, and then propose the LIHTC idea - with a LIHTC representative in tow, maybe.
Anyway, I mention Crescent City because in case the thinking is the town is too small for these investors, it definitely is not, if they build them in such a small, low income area as Crescent City. It's a very poor area overall. I doubt Chelan is, but at any rate, it's not too small for these investors to consider.
I know it's a pain and can feel exhausting to go up against such frustration. You need to vote in a new council. It can be changed back, it will just be a pain. I sure wish you the best. So frustrating to work so hard at building something successful and having a group of nutters mess it up. I feel for you.