There are spots of 30-40 feet of depth right next to shore on the straits where I can almost guarantee big chinook to be at dawn and dusk during season, and have taken plenty of neophytes out there to prove that over and over with success using cut plug herring in those days. I agree that even with a 400-500 grain line or LC-13 and the right fly worked deep or up and down the water column you will score the big tyee on the fly rod with some regularity once the tricks are figured out.
For instance, even though the depth of the water is 120 ft at the green can, the kings can be in the first 10-20 feet during the outgoing rip. There are inlets on the south side of Vancouver Island where the tyee are caught in 20 feet of water - that's all the delta has for depth!
Willapa Bay - about 20 feet deep.
The rocks off Wadah Island at Neah Bay constantly have chinook running bait against the rocks and spraying them out of the water in the morning and evening.
Kenmore area, shallow huge kings. Olympia area, south sound; Nisqually delta, the rip at Point no Point, Dalco, Bush Pt - a deep twitching retrieve with the outgoing rip pushing north toward the bluffs,
Kids fishing buzz bombs off the rocks by the kelp beds at Clallam Bay catch huge kings regularly.
You're right there has to be a way to do this, and I wish you the best of luck figuring it out. I only wish I could do it with you!!!