New to WS and new to this discussion. Forgive me if I am rehashing things already discussed. Some thoughts...
1) The odd gait of this person seems in part to me to be affected because the person is walking consciously on his/her heels. Notice how weight is never placed on the toes. Most likely, as some others have suggested, because the shoes are larger than the feet. Try it yourself. Walking on your heels like that and turning a foot out will definitely give you a distinctive gait - and hide the way you normally walk.
2) The tool that this person is carrying appears to me to be a
5.11 multisledge. Tactical gear designed for forced entry and could definitely be a terrible weapon. If it was truly left behind, then the killer seems not to be concerned that this kind of gear can probably be traced by purchase history. Does anyone else agree or have a definitive reason it is not this item?
3) The storm that night, the small amount of time between her death and the arrival of the first CG-er, and the fact that there is only one driveway entrance/exit off a major highway makes one wonder how this person entered and exited the church grounds. Driveway seems overly risky, and given the amount of care this person took to protect his/her identity, it seems unlikely. But equally unlikely is it that he/she would choose to leave foot and/or tire tracks in the mud to go toward the airport or through fenced fields on either side to get to transportation.
4) Though this is probably a stretch, I've wondered if perhaps Missy became caught in someone else's road rage in or on her way home from Austin (not long before her death) and the offender was patient in exacting revenge. The person could have been in LE somewhere or have access to new license plate databases and looked her up (hopefully LE has already researched if anyone did so) and then plotted the deed.
Stay safe out there...