Okay, I've decided to rotate all the switches back to 0 or 180 degrees.
Unfortunately, there's one which cannot be rotated like this no matter what, so the ISO enter will be rotated 90 degrees and it'll be the only one.
Except for the 6 pins with SPI, I'll break out the 4 unused pins and all 5 row signals. This will make it possible to extend the board with extra keys or connect extension modules.
The GHPad can be connected either using 2 of the extra pins, or directly to the matrix using all four pins as columns, in which case it won't require a separate controller.
Now the question is: where to put the breakout pads?