It seems like the CM4 design was almost made with laptops in mind. The main issue is cooling, though. The case would need to insure that some sort of heat sink would maintain physical contact with the SoC, and some thermal paste would be a good thing as well, so this might be a little more than "drop in a new module." Otherwise, throttling will be an issue with any sustained work. How much of a problem that becomes depends on the intended use.
It wouldn't be an M1 Mac, but an 8 GB CM4 could still be the heart of a nice low-power laptop, with the bonus of GPIO pins, as long as the cooling is sorted out.
I've got a side project where I'm building a tablet based around the CM4, and one big issue is that none of the RPis can suspend to RAM. If I stick with the CM4 (I may switch to one of the two rk3566 boards mentioned in TFA, which hopefully support suspend), I'll probably end up having my tablet suspend to disk.
The Pinebook pro just uses a thermal pad touching the IHS and the magnesium bottom panel. It works fairly well but will still throttle significantly under a full load for long enough.
Could you just air cool it? I thought pis were supposed to tolerate passive cooling in general, so I would think it would be enough to have a fan to offset the case
Running at 1.5 GHz, air cooling is enough. The Pi 400 has a massive but thin heat sink that keeps it running well at 1.8 GHz (and I overclocked to 2+ GHz with no ill effect or throttling).
If you have ambient temps under 80°F and a light breeze past the bare SoC it doesn't seem to throttle unless overclocked to 2+ GHz.
It wouldn't be an M1 Mac, but an 8 GB CM4 could still be the heart of a nice low-power laptop, with the bonus of GPIO pins, as long as the cooling is sorted out.