CPU slot is a nice to have.
One way to use it would be to have a modest & cheap CPU on the motherboard and a CPU slot for CPU upgrade (heterogenous) / second CPU (heterogenous / assymmetric multiprocessing).
I'm afraid that in the very low cost models CPUslot is not possible, but in high end models it would give an easy way to build a lot of different performance computer models per need.
And if the CPU slot is open for CPU card manufacturers to compete, it would accelerate CPU price drop & adoption of the latest & fastest CPU technologies....
(what is currently stopping people from instaling macintosh megarray CPU cards in A1XE???)
btw. Would CBM have survived better without competing CPU card manufacturers?
Would they have made more money by providing a new motherboard every few months instead of letting CPU card manufacturers to flourish...