For that matter is there any reason the cameras they use on something like the quest couldn't use the lighthouses? They see IR do they not?
To me it seems like they best option would be to have the vision based slam be the default tracking option but then have the upgrade option for something like the lighthouses to improve accuracy, allow FBT, or to have tracking where it would otherwise fail.
The cameras by default have a low refresh rate but surely you could even increase the frequency lowering the resolution since you only need to see the laser sweep. I'm not sure what the current sensors ping at but they can't be all that fast right?
I was kind of surprised they didn't take that approach for the index.