Water and slopes are not a good combination for road safety even for four-wheelers.
If you want to know the alternative, cross reference the Denny regrade (for historical precedent of making the hills safer to scale) and the West Seattle Bridge (for current frame of reference of how a relatively small infrastructure project has a huge impact). Nearly all of the roads heading east out of downtown have a high grade somewhere uphill that drivers struggle with even on dry days. Gratefully most of the worst car routes aren’t major bike routes.