I'm really quite pleased with myself and wanted to share here. So I found myself with no solution for an e-brake/parking brake and came up with this.
Basically, I went with a foolishly high horsepower motor (497 rwhp based on last dyno run) and needed heavy custom axles and therefore needed to use an STI knuckle. The STI knuckle I used was from a 2004 STI since I wanted 5x100 to match my wheels (which I'm going to replace anyway, so turns out that was dumb). Anyways, the STI knuckle works with the WRX-intended big brake kit from Wilwood so long as you don't try to use the e-brake setup. (The Wilwood big brake kit, I purchased from Factory Five but its intended for a 2007 WRX, not an STI).
So, that's a long story to say that I now had a car with 6 pot fronts, 4 pot rears on a 12.88"x1.1" rotor and no parking brake.
Then I thought hey, Wilwood makes an MC4 mechanically operated parking brake caliper. I'll use that. I order them and it turns out it only fits a 12.88x0.8" rotor. <sigh>
So I extended the caliper bridge to fit the 1.1" rotor and made a custom mount and I'm very happy with the result and look!
Anyways, here is the car and the parking brake setup works mint!