This is a situation where the SWC typically arrives early and has to sit until the scheduled 12:32am departure. The train leaves Kansas City at 10:55pm and the run to Lawrence is only 40 miles, so a midnight arrival may be typical. This morning (6/16), for example, #3 arrived LRC 12:01am then sat until the 12:32am departure. 6/15 arrival was at 12:09. 6/14 it arrived 12:06.
The Southwest Chief uses BNSF end to end.
EDIT: Let me add one more thing. This idea for a 9pm arrival would be nice, but I am willing to bet that there may be a few passengers on board for who may not see the charm in bands playing outside the train at midnight. For a college town on Friday night, midnight is still early. For some of the demographic groups typically on Amtrak long distance trains, midnight is the wee hours and they may not be in the mood to be "serenaded by voices, guitars, and banjos of local bluegrass and old-time music performers."
You know, the more I think about this, the funnier it gets. I have this picture of the train silently pulling in at midnight, the quiet solitude suddenly broken by a band belting out some bluegrass at full volume, and an entire sleeping car being startled awake. Priceless.