I'm rereading my post and I think I forgot to mention that I had to create an identical spline (a backwards track) to run the opposite way. See as far as I know, the splines only have a starting point. From anything I've tried, they don't seem to support and kind of inversion methods. This runs in line with what Obsttorte was saying about using a spline for what it wasn't meant for. And believe me if I could find a smart and compact way for node based pathing to blend turns and pitch, I'd use them in a heartbeat.
So I'll back up a tad bit and explain what's causing that whole flip dilemma... .removeInitialSplineAngles()
This command is perfect for taking roll out of the func_mover_amodel. However, it has the unforeseen side affect of inverting pitch axis. Meaning you flip the wrong direction when moving on the same path (in reverse). This however is remedied by commenting out the, removeInitialSplineAngles() but then we return back to unpredictable roll on turns as well as the model realigning to face the newly introduced spline direction. My untested theory is that it may be resolved if the same model is mirrored (saved as an additional mesh) and toggled back and forth when either matching courses are plotted. It's too bad there wasn't a ready made command to just run a spline backwards, but I supposed floating cameras in DooM3 might have looked odd going the wrong way.