MILW built the station in 1965 to replace an ancient station, and C&NW moved in shorty after in order to dump their ancient station on the lake. It really is a decent mid-size city station for 5-10 trains per day plus intercity bus. Amtrak has never had another station. MILW was a few blocks west, and C&NW was way north on the lake by downtown.
Of those five tracks, only two go east. All five go west. One stub is used for private cars. But there are open ends for tracks 3 and 4, and if they can make the radius onto the bridge, they can be connected to the east. But I think the problem is long road freights going through on tracks 1 or 2 probably move very slowly between the bridge, curve, and station. In other words, this station could have 20 tracks and a slow moving freight on track 2 blocks most everything for 20 minutes and ruins the timekeeping of a 90 minute Chicago run.
As for Metra, this is a 90 minute run that mostly carries commuters. But Amtrak thinks it is the 20th Century limited, so you have to line up for boarding and go through all the officious crap, then march to the train, use one of two open doors (of the ten available doors). Amtrak does not notice that two track over, Metra boards 1000 passengers per train without any closed doors or marching games. I detest the Amtrak games one has to play. If this were a Metra operation it would be so much simpler (and more capacity in bilevels) to operate.
Amtrak is proud to announce a new train to Florida that doesn't stink: The Floaterian. An all-star just like Babe Ruth.