>>319006434
I mean inside out cameras on the trackers themselves. 
global shutter cameras like the ones in the quest 2 are pretty cheap, surprised nobody has tried it yet. 
The tracking on a WMR headsets 2 camera stereo pair is actually really good, it's the controllers that rely on a light ring that are the problem, not the headset, where the tracking is actually better than lighthouse due to basically 0 occlusion possible.