Zombie-thread, I know, but this thread got me started down the path towards figuring this all out, so I figured I'd post here to inform.
The RevB/RevQE compatibility for the xd60/64 effectively means trading in your backlight and RGB pins for extra columns.
From the QMK xd60.h file, we have the GPIO pads:
/* XD60 LEDs
* GPIO pads
* 0 F7 not connected
* 1 F6 RGB PWM Underglow
* 2 F5 Backlight LED
* 3 F4 not connected
* B2 Capslock LED
* B0 not connected
Pins F4-F7 land on expansion pin-out at the top of the board (cluster labeled P5). From top to bottom, they are F7,4,6,5.
So, if you disable backlight and RGB, you can list F4-F7 as columns in your config file. Then, using the row pins (right side of the board, labeled P6) you can add up to 20 extra switches to your keymap.
I just finished compiling the hex, and have only tested with a wire (no diodes and switches) but you may need to desolder or cut the RGB trace, as I had some voltage backfeed to an LED.
Source:
New features section:
http://blog.komar.be/gh60-evolution/
GH60 Schematic:
http://blog.komar.be/wp-content/uploads ... -06-02.pdf
The pin-out was slightly different than the GH60 (2 of the GPIO pins were put to use) but it seems to work.
Happy clacking.