First off, why has Lake Stevens allowed so much development without the inner structure to support the development? As a thirty five year resident of Lake Stevens, the roads have become overcrowded with little improvement to the roads. Kind of the cart before the horse. If it where not for out of control development there would not be such a problem with the trestle.
Second off, the problem at this point is not the trestle but merging on and off the trestle. Increasing capacity on the trestle will create a extensive back up merging on to I-5.
I would hope that the engineers have a solution, but after reconfiguring the I-5 corridor though Everett for the 2010 Vancouver Olympics, which created some of the worst traffic in the state, I have little confidence. And yes, I hate sitting in traffic on the trestle. I remember a time of reasonable commute times.