While trying to tune the values of v.2 so that it was a bit more responsive I had an idea for doing it that seemed to make a lot more sense. Trigger Capsule!
I should state here, that this is where I had originally stopped writing this post before actually implementing it. After a fair bit of work, I got the CapsuleCapture version of RIPmotion "working". I ended up hating it and abandoning it, but I figured it's worthwhile to describe it here for posterity. If you aren't interested in learning about a failed technique, I suggest you stop reading here.
So basically, the idea behind this was to overcome the limitation of v.2 where it was limited to head motion in a specified range from the initial head position. My idea to do this was to have a capsule trigger follow the HMD, so movement would be recorded only when within this capsule. This way, if you squatted down and started "running" then it would detect it and propel you forward. This was clunky, slow and overall not what I expected.
Oh well, on to the next one!