It started with notebooks, but that wasn’t the master plan.
You’d obviously have to design the laptop around the battery and not just retrofit it in. Make it a bit thicker, make it a bit longer? The 16" already isn’t a small, thin, or light laptop so the little extra room needed wouldn’t make that much of a difference.
Longer doesn’t work because it has to fit in existing bags people have. Thickening it won’t work because reviewers will then complain it’s too thick.
I have a Toshiba laptop from around 2012 which has a slide-out optical drive. To me, it’s thick but not too thick; it’s just right. If we could return to that size, I think we’d be good. It’d also support better cooling (my Framework 13 with an i7-1280P gets hot, and there just isn’t enough space for a bigger cooler). Reviewers over the past 10 years have pushed for thinner and thinner, and we gave up too much in the meantime.
Same goes for screen bezels and built in webcams. All else being equal, a cam with a bigger sensor is better because it can capture more light. Thin screen bezels force a small webcam, and thus your laptop has a shittier camera than a 10 year old smartphone.
In both cases, I don’t think actual customers care all that much past a certain point. Reviewers have been deducting stars for a slightly thicker case or a slightly thicker bezel than other models on the market, and customers just go along with it.
Thickening it won’t work because reviewers will then complain it’s too thick.
I’ve used thicker laptops for years and had no problem whatsoever with them in that time.
I suppose that there’s some theoretical thickness where a laptop becomes unergonomic, but my desktop’s keyboard is far thicker than my laptop’s, and it’s got no constraints other than being ergonomic.
Is someone using some kind of incredibly-thin carrying case? I haven’t seen that. I throw my laptop in a laptop backpack. It could be probably at least three times thicker and still fit in that.
I don’t think people looking at Framework care too much about reviewers. They’re targeting DIY enthusiasts, which are also the type that’ll probably be reading the measurements and whatnot themselves.
The do have to source the same parts as the rest of the industry. This is why, for example, they can’t have a socketable laptop CPU. Those don’t exist anymore, and Framework is too small to afford a custom part from Intel or AMD.
Same with batteries. A thicker laptop battery may not even exist.