Just a wierd thought - and no time spent thinking schedules.
When I look at the map, everything from MSP goes to CHI and then CHI it branches out.
How about a circle route? Two trains - going opposite directions.
CHI - in MO or IA - MSP - CHI
This would give MSP a line to the south w/o going through CHI, and provide MSP-CHI service.
You triggered a chain of thought: There
is a routing through Chicago you could probably work out to get an MSP-bound train out the south side of Union Station. It would involve a mess of negotiating...probably with the Belt Railroad of Chicago (BRC) and the Canadian National (CN). You're probably adding time to a trip, but again...if MSP were the overnight segment, this isn't an issue.
Circling back around (pun intended), CHI-IND-STL actually comes to mind as a theoretical "circle" route to supplement the Hoosier State/Cardinal: Down to STL in the morning, STL-IND in the afternoon, and IND-CHI in the evening (and the reverse). It's a bit under 750 miles, but I think this would be a decent one to throw at the states when times improve: You'd get IND-STL service, you'd get decent IND-CHI service, and you could probably use the non-STL-KCY trains to make this route work. I'll go ahead and say that I highly suspect that the STL-IND run would be the "ugly duckling" if you don't have any through cars to/from the Cardinal (and I don't even want to
think about the logistics of passing cars from the Cardinal to the Loop to the MORR). Assuming you strictly ran the loop, departures at 7 AM with an average speed (stops included) of 45 MPH would get the train back about 11:30 PM or so...actually a substantial improvement on the current IND-CHI service in terms of timing.
Assuming you wanted to do this, I think you'd only need two new trainsets: Just start one trainset in CHI, one in STL, and one in IND each day going each way. Two of the six would be from the STL-CHI run and two would be the Hoosier State set. When you need to bring them in for maintenance, you swap a set out in Chicago. You've already got staff spending the night in IND and STL as it stands, so...this isn't much of a leap. You could also take a car or two off the Cardinal to STL and return the cars the same day on the evening train a la the Boston leg of the LSL.
Edit: I hate getting these bugs in my mind. Ok, sample timetable:
Depart CHI: 7:00 AM (currently train 301)
Arrive STL: 12:20 PM (ditto)
Depart STL: 12:50 PM
Arrive IND: 5:00 PM
Depart IND: 5:30 PM
Arrive CHI: 10:30 PM
All times are Central.
Depart CHI: 7:00 AM
Arrive IND: 12:00 PM
Depart IND: 12:30 PM
Arrive STL: 5:00 PM
Depart STL: 5:30 PM (Currently 306)
Arrive CHI: 11:10 PM (Ditto)
All times are Central.
I'm assuming about four and a half hours for the IND-STL segment. Once the CHI-STL line gets upgraded, you could probably knock 20 minutes off of that segment and give it to STL-IND for buffer (that would give you five hours to work with).