Sooo I guess the SPI bus to this thing is going to be write only.
The instant I configure the MISO pin in SPI mode, it no longer is acting as JTRST. And the JTAG interface resets and I lose the ability to program the thing until I manually stick a wire across the RST# pin and release it while racing the firmware and JTAG dongle trying to hold the chip in reset before it reaches the point of enabling the SPI interface.
Good news is, there's nothing to read back from the front panel anyway. The power and reset buttons are raw 3.3V GPIOs and the remainder of the SPI bus is entirely FPGA -> MCU traffic.