Seems like a vendor finally got around to making a Ti specific rear kit using wilwood calipers. You can choose to use either the forged superlite 4, similar to what I have on the front of my car, or you can use the lighter dynalite caliper. But it would allow you to upgrade to rear vented rotors.
I emailed the guy making this kit and his take was that to use this properly you would need a brake bias valve to adjust the front/rear brake bias.
http://www.massivebrakes.com/home.html "12.2" x 1.25" lightweight rotors (UL) and either Superlite (1.12" pistons) or custom SL4R (1.12" +1.25") calipers."
318ti rear BBK 
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