Given the fact that CM5 has identical hardware factor with CM4, can’t we just replace the module?
I did once to replace the installed CM4 with one with more RAM/Flash, after the reTerminal specific device tree overlay was installed, it just works. The whole disassemble/assemble process is quite easy without needs of special tools.
The only thing unknown is that the perpheral compatibility, but according to the wiki, all of them are already supported by Linux so I guess we can tweak some device tree files to make them work.