So using a bit of relatively simple geometry and some Python scripting in Maya, I worked out a way to quickly create basic, easily tweak-able foundations for walk-turn animations.
In the video above I'm just blending between 5 animations, a walk forward and a fast and slow turn in each direction. The animations are actually done in place, the displacement is all on the master control, so the feet slide a bit when they are blending between animations, but in a game engine, it should be quite easy to clean that up with a bit of IK.
The short version is this: we start by baking all the IK/world space animation to locators (i.e. the feet, hips and shoulders, but not the tail, head, clavicles, etc.), create a rig that turns the forward translation into movement around a pivot point (so that the controls will move along the edge of a circle instead of in a straight line), and then bake the result back on to the control rig.
So, I'm going my scripts and explain how they all work, but fair warning, it is going to be a bit boring. If you're an animator and you've never done any scripting, this might be a good place to start? The first and third script have a lot of general utility and there shouldn't be anything too tricky (except maybe world space matrixes, but I'm just using those as a way to set the rotation, position and scale).
Anyways, if you are interested in Maya python script things, read on. Look, I even made some little shelf icons: