First, forget about changing the I-5 system from south of Woodland through I-405. Can you imagine the disruptions that would happen for years of construction to build a new bridge? To go east from I-5, most drivers go over the bridge down to the I-84 interchange. The gridlock can be disastrous.
Second, start a new elevated road going southeast to Camas/Washougal, build a bridge across to Gresham/Wood Village in Oregon. This route would take delivery trucks going east off the crowded I-5. This route could be a toll road.
Having it be elevated could save money because not as much private property would have to be purchased.
The I-205 freeway and bridge would benefit this new route also.