Well put Gary, I think you've help me understand braking systems a bunch more. I think the failure in our earlier discussion was a result of a brake-centric train of thought over a tire-centric train of thought. Basically we were tracing the effects of the brakes on the tires, rather than the effects of the tires on the brakes. Couple that with an incomplete understanding of a tire's dynamic to static friction transition, and I think you can see where the pin-in-hole brakes came from.
Taking a step back regarding the sizing of pistons in the front brakes to match an existing rear caliper, how is that different from using a brake proportioning valve? I'm not quite sure how a valve would work on a WRX due to the RF-LR/LF-RR dual circuit nature of the WRX's brake system (two valves?), but I infer that they're quite popular for tuning the brakes on solid-rear axle cars that use a front/rear circuit. Is there some drawback to using a valve? It seems the ability to adjust brake bias would be very useful! Plus, you could potentially lower your initial brake purchase costs by not having to have custom pistons up front, just get the less expensive, mass produced calipers, and adjust the bias w/ a valve.