Slim, lightweight form factors similar to that of the Bigscreen Beyond are not going to be practical in a self-contained headset for quite some time to come, at least if the goal is to play anything more demanding than Terraria on it and its price range is anywhere remotely within reach of the general consumer.
The only reason why Facebook has been able to swing such low prices is with steep subsidization, and the Quest hardware itself isn't much less bulky.
I hope the fact there's now a more open, Linux based VR headset will encourage more variety of headsets and price points, like we see with PCs, generic Android handhelds, etc.
I'd love someone (maybe even Bigscreen themselves) to make something like a standalone version of the Beyond 2. I'd be happy with some kind of puck or whatever for the compute and/or battery just to have it be that lightweight.