Hello,
I have PZ5064 CPLD to read and reprogram.This have address and data pins and internal logic, so I guess it won't be possible for me just to add as a custom chip.It's the same chip as Xilinx XCR5064.
There is datasheet for Xilinx XCR5064C but it's a version that have JTAG. Xilinx XCR5064 doesn't.