Q-switch will be a nice addition and the new harness should fit, too.
The 83 Distillate I used to own came in a trapezoidal case similar to yours, it was a nice case. I also thought the shape was preferable to a rectangular case. One of the guitars I own came in a custom Mark Leaf case that is also trapezoidal in shape, really nice case, water- and air-tight with a built in hygrometer.