I've further decided that instead of cutting apart the original dash bezel parts, I'm going to cast duplicates out of polyurethane resin (plastic), using silicone rubber molding materials instead, and modify the duplicates.
The parts that I would have had to cut are:
66065E $52.26 Panel-audio (radio bezel)
66065O $70.50 Panel-center (center heat/ac vents w/hazard switch)
66080 $33.62 Console-instrument panel (the lower center console itself)
The parts are listed here, and are shown in the 2nd and 3rd diagrams:
Rather than modify/destroy $120-150 worth of parts, I'm going to make exact duplicates and modify those instead..
I'll be cross-posting a thread in Fabrication with pictures tomorrow, I have to pick up the casting materials tomorrow morning.
The upshot of this is, if anybody else wants to put a 8.4" LCD in their 2002-2004(maybe) Impreza/WRX, I'll be able to cast a perfect part easily.