Many good points there Rich!
As for the Zetecs, since I have not really had a good chance to look at there configuration, I can't really comment on what could be done. But I do have plenty of ideas of what might be possible.
As for the Duratecs, GMK (Grand Master Kane, from over at NECO) has already designed a true cold air intake kit. It's actually pretty nice, because it does not require that you relocate the battery to the trunk. IIRC, you have to make a few small cuts on the battery tray and cut a 3" hole in the body located under the battery.
Here is ZetecNinja's Zetec w/GMK Intake Tube
Here is the GMK intake tube in Carbon Fiber (pics curtousy of Bridge)
And here is one installed on a Duratec Cougar
As for addressing the issue of the ambient heat from the engine bay, soaking through the intake tube material? Two options; 1)Apply exhaust wrap to the tubing, 2)As mentioned my Warmonger in my thread, apply a thermal coating to the inside of the whatever material that is exposed to the heat.
I will agree that my heatsheild is not a sheild. It really is more of a reworking of the air box itself. But by just removing the flat panel filter, you straighten the path in which the air travels to the TB every so slightly. I assume this is the main reason the SVTs used the design of filter it did and not the flat/panel style that was found in the SE design.
The main reason I decided to make a box and not just a sheild is because I saw no benifit from any of the other designs out there (just be looking mind you). I'm not sure if it was a smart move, but I am happy with it none-the-less. The only problem I have had with it, so far, is I tend to pick up a lot of trash over a period of time. Everytime I was my car, I clean the box out and I find all sorts of leaves and such. I have even pulled small pieces of cardboard out of it. So I need to make some sort of something, at the base of the fenderwell, to block all this stuff.