I know this is late, but would the western, "plain" work. No embroidery on it. Just boot an leather?
The app team has the final say, but I think plain ones would work, and would love to see ankle boots like these on a kit:
As long as they have some spats or armor over the ankle area, they might be totally fine. They're almost Cad Bane levels of subtley Western, but without specifically Earthy detail, just the correct "shape". I'm almost considering getting some like these for my kit, now...
I'm not sure that the higher "cowboy" boots would work, even without the bells and whistles, as the curved upper cuff is just too recognizable as "cowboy shoes." A taller boot would have to be something with a more military look, a Han-Solo-style riding boot (that is what cowboy boots are, after all...) or a harness/biker boot. Something like this comes to mind, but with more armor:
Anyone who actually has say in what gets approved, please chime in! I'm super curious if they would work, as well.