Detour through Tulsa?
Tulsa's Turkey mountain is worth checking out. It is just off of highway 75. 61st street exit, head east to Elwood (just south of 75/I-44 interchange). You could go 75 to I-44 to 71 to get from Dallas to Nevada. Turkey is a spiderweb of trails. You can do a few loops and periodically stop back at the parking lot. There is also a great variety of trails. For December, some of it may have ice, snow, mud, etc., but there is always part of it that is rideable. I highly recommend stopping by.
The Womble would be well worth the time to go check out, but it would be a bit further out of your way than Turkey Mountain. It's also a long non-loop trail in the middle of no where. Not sure I'd take the time to stop there in December. If there is too much snow, ice, mud, downed trees, or whatever in a particular area, you can't just re-route on another trail. Going from Dallas to Nevada, you might choose to go to Mena rather than Hot Springs. Neither are actually on the trail, so you'd have to go toward Mt. Ida or Sims, and find a trailhead. This is a very rural area. Have a map and a plan before you leave Mena or Hot Springs.
Not sure the type of riding you like? Turkey mountain and The Womble are much more demanding than RCP or Erwin or anything else in the metroplex. If you describe the DFW metroplex trails as "really good", maybe you would be interested in crushed limestone rail to trail stuff? I think you could pick up the Katy trail somewhere south of KC. That would be a fun ride - although not really "mountain biking".
My sister used to ride someplace in Warrensburg when she went to college there. Sorry, I don't remember the name and I never rode it with her. I also have run into some riders from Springfield. Don't know what trails they ride, but I'm sure if you stopped in a bikeshop, they could tell you.