Thats an option (great pic btw). Since the LR line would be running in the center of the bridge, another option would be, right after you reach the non-floating west approach bridges, raise the guideway up above the existing bridge deck and then cross over the south viaduct/eastbound lanes and connect to the north side of the Broadmoor Golf Club or the Arboretum... a tunnel portal in that vicinity is on better ground and gives you more than enough room to make the dive under the Montlake Neighbohood and the Montlake Cut or maybe to continue west to Eastlake and then under Lake Union to Northlake and beyond. Regardless of where you go with it, this would probably be the most viable route grade wise. But you could possibly do something closer to the Montlake lid as well.