I enjoy getting off Interstate and taking my time and although I don't know much about heading back east, we did enjoy the drive along US380 ('Billy the Kid trail') through Capitan,(Home of Smokey bear) Fort Stanton and the historic town of Lincoln. It depends on how many extra miles and time you want to add.
I don't know about nicer and more scenic, but you can make the drive on mostly non-Interstates by adding a few hours.
Take I-25 north to Springer, get on US-56 east.
At Hugoton KS, take KS-51 east to US-83 north to US-160 east to US-54 east.
US-54 merges with US-400, stay on US-400 through Wichita.
Just west of Fredonia, take KS-39 east to KS-7 to US-69 into Fort Scott.
Take US-54 east to Jeff City, then US-50 most of the way to STL.
I like the thought of that route that GLC suggested, but I would like to give you a bit of warning. After you take the bypass around Lake of the Ozarks, there's a lot of construction just before you get to County-Rt W. They are making that into a freeway style intersection, because it's been a bit of a hazard -- a traffic light that comes out of nowhere after miles and miles of freely moving traffic. Daughter says that there's a lot of construction, but it shouldn't delay you any.
If you're going via US-54, you might want to stop and see a bit of the Lake. You can drive the 'old road' through town. At this time of the year, there won't be much traffic at all. Drive the Strip, cross Bagnell Dam, follow the signs back to US-54 (it takes you back via that annoying intersection).