The finished product. Wires tamed slightly.
I could have gone farther with the wiring cleanup, and I meant to originally, but at this point, it was 1 in the morning (actually my third 1 in the morning in a row) and I was done. Some zip ties help to group the cables a bit. I'm not sure how to clean up the Remora wiring harnesses, but I stopped caring at 11 pm, I think. Still, I'm very pleased with how this turned out.
If you zoom in a bit and look at the Remora board, you'll see that the board is just slightly too tall to fit underneath the buttons in a FightStick Pro body. I had to angle the board a little bit so that the tip of it fits between the Seimitsu button and ArcEye3 of the RT button. But this is a small thing and no electrical connections are touching, so I'm satisfied.