This could be reasonably possible with Apple silicon—well, maybe not 3lbs, but noticeably lighter than the current model.
Part of the reason the 16” is so heavy is the 100Whr battery (which still manages to be woefully inadequate due to how much power the CPU sucks, let alone the GPU).
The 13” ASi Pro has a 58Whr battery for “up to 17 hours” use, which seems to pan out to about 12-14 hours real-world usage. They could put that exact battery in an ASi 16” and it would still be leagues better than the “up to 11 hours” battery in the current model, which in my experience is actually 3-5 hours.
> and other manufacturers have entries in that range.
The one that comes to mind is the LG Gram series, of which they make a lot of compromises in order to accomplish their weight goals. Opening up the chassis of the LG Gram 17 and 15 you'll see a lot of empty space and a battery that is much smaller than it could accommodate. I think it'd be doable if apple made a 16 inch variant with the m1 chip in it but I'm not sure that you could without making similar compromises that LG does.
Personally for a 16 inch laptop I'd rather have longer battery life and processing power which I think more closely aligns with people who prefer the larger form factor anyway. Still, it'd be nice to have options!
For whatever reason this idea always gets downvoted but I believe it will happen someday and every who downvoted will suddenly "get it".