I had an X62 (upgraded motherboard in an x60 shell from 51nb) and my brother had whatever the upgraded X220 was, but they were a little flaky. Super cool though.
AIUI the thermal design is the blocker with modern chipsets. Usually it's really carefully tuned along with software to dial in the right performance/battery life/longevity/safety metrics, and that's a different skillset than EE'ing a new board.
> The thing about a Pi 5 though is that it is really not any faster than the X220 natively.
It's generally faster [0] but I mean, it's the Raspberry Pi experience. Battery life would be much better, though. I understand people wanting a "modern" X220, but a big benefit for me is that I can't write junk slow software on it, so something circumspect like an SBC is ideal for me. Plus I love the idea of slapping a new CM in there and everything getting better.
> speakers are still top shelf
I'll confess to apostasy: I bought a 14" M1 Max at the end of 2021. Although it's quite different than the X220 it's a great machine in its own right, and one of the ways it's objectively better is its speaker system. It's bananas how good it sounds. It's a computer I hate to love, but I agree the Apple Silicon laptops are probably all time great laptops. I"m tempted to say they're maybe even on par w/ the X/T series 2005-2012, but they're essentially not user serviceable, and in particular I'm skeptical the keyboards and storage hold up over time, so we'll see what the used market looks like in a few years.
[0]: https://browser.geekbench.com/v6/cpu/compare/12009065?baseli...