Back in the 80’s, when memory came in DIL packages, we used to stack these on top of each other, just bending out the chip select pin and wiring this to a little decoder chip on the top of the stack. Eight memory chips plus the decoder was the largest stack I used to make (and sell).
I always wondered why the chip manufacturers didn’t do this themselves.
Oh and don’t say that the [PCB/chip] stacking is too difficult, I’ve been buying 24 layer PCBs for 6 or 7 years now (sequential build, 3 sequences of 8 layers). Mind you, only one lab in Europe could make them successfully!
Mine's the one with the spanner in one pocket and the big 'ammer in the other!