It’s not really a matter of CPU upgrades, though that could be nice. It’s a matter of field-replaceable parts.
We see problem after problem with CPUs. Some of them can only be fully fixed with hardware replacement, rather than firmware changes. Intell has promised new CPUs without the Spectre vulnerability; but if the CPU in your laptop cannot be replaced, you will be out in the cold.
The CPU needs to be be replaceable with a compatible, bug-fixed CPU.