CPLD use with 6800 processor
Could a CPLD inline between the CPU and ROMs, adding between a 7ns and 25ns delay adversely affect the CPU running at that speed?


Almost certainly not. 25 ns (worst case) is roughly 2% of your system's cycle time. It's negligible.

Low clock frequencies (under 1 MHz) on older systems are often generated by RC oscillators. If your system is using one, it probably varies by at least 2% with temperature -- meaning that your system certainly has at least 25 ns of slack available.