Add more Kokanee, get more, bigger bows, with more people spending more money to catch them
I can't comment on the 5 fish limit, I don't know angler days, retention, or other factors (and even if I did, the math on that it sounds like a headache). I do know that there were more nutrients (and ecoli) entering the lake before better sewage systems were put in place and this could have bumped up productivity substantially (OLAP reports speak to this). Urbanization and damming of water courses, curbing of septic and other anthropogenic effluent, and mysis introduction have changed the lake. I agree with you that more kokanee, bigger rainbow, and increased angler effort and economic boost would be great, I'm just not sure the answer is as simple as a hatchery.
I flogged the lake south of the bridge yesterday and managed 2 nice healthy bows in the 4lb range. I don't know how many times i changed lures but it doesn't really seem like they are hitting anything in particular. 1 on a cop car coyote down at 28ft and the other on an old red and silver plastic j-plug at 58. Almost every fish I've caught this year has been on something different. Surface temps shot up 8 degrees yesterday. Lots of debris floating around. Rod Henning was out down south and he caught pretty much the same as me. With the temps heating up, the fishing should get a little better. I've had my most luck when it's between 48-54.
Blue/red/orange on sunny days and white/grey on colour days.