Because the people we pay millions of dollars to find a solution can't find a good one, I'll just give you one for free.
Build a separate bridge. You're planning on making one alongside the highway bridge anyway. Have it run parallel to the river for awhile so it can ramp up to go across at a high level and a grade the MAX can climb. Do the opposite on the other side.
You surely have two problems with this:
(1) This will cost more.
(2) This will make an inconvenience for riders to
take time to make the loop.
But I answer with these suggestions:
(1) The longer you government people take to bicker
about the bridge being too low, you could have
built this by itself and be running MAX across it.
And it would probably cost less than being tied in
(2) I ride the Blue Line around the loopty-loop at
Sunset TC all the time. I'm used to it. We have
another in the Red Line looping under itself at
Gateway. I don't hear people complaining about
either of these.
Problem solved. And you just saved millions in the planning phase by reading this here.