The highliners are gallery cars. The old St. Louis highliners are a bit different in design but still have the gallery concept. The newer Sumitomo cars are just powered gallery cars - otherwise they're on the same plan as the gallery cars at Metra, Caltrain, and VRE.
As for suggesting AC for Metra new-build electrification, I believe it's significantly cheaper for new-build electrification than the traditional high-voltage DC used on the IC and South Shore. As the lines do not share equipment, it would probably be cheaper to do AC on any new builds. Further, rather than buying all new equipment, an off-the-shelf ALP64 or Siemens locomotive could be bought to pull existing gallery cars rather than buying hundreds of MU's.
Were the entire system to be converted to electrification on a common voltage, it would make sense to use MU's on locals for acceleration purposes and locomotive-hauled consists on limiteds, especially longer ones. But that's really stretching reality. That money just doesn't exist.
The new Acela: It's not Aveliable.