Design challenge: a complete IBM PC XT compatible system using a stack of 8-bit PC/104 boards. Period correct components not required, i.e. modern CMOS versions of most main chips, NEC V20HL, 0603 SMT passives, 74HCT series logic in TSSOP and programmable logic in TQFP, AS6C4008 as main memory, etc. No more than 4 layers of copper allowed, but up to three layers of components allowed, including putting SMT components underneath DIP sockets and putting SMT components to the back side of the board.
Failure: Even with double side components and putting SMT components underneath DIP sockets allowed, even after condensing 82C88 and 82C84 into one EPM3064 CPLD, squeezing the three DIP-40 chips (80C88, 8087 and 80C37) and the 28C256 BIOS ROM chip into PC/104 is still likely impossible.
Mitigation: Maybe I should split the core complex, equivalent to the first few pages on the IBM PC/XT schematics, into two boards: 80C88 + 8087 + 82C88 + 82C84 + 82C59 on one board, 82C37 + AT28C256 + AS7C4008 + 82C53 + main CPLD on another. The two boards together implements the full ISA bus, and some additional pin headers would be used to link the internal signals together.