Yep, thought about those. There are one or two similar ones (one that is supposed to be watertight, too), that I have found that people have used. Been surfing Google for a while now looking for ideas before I posted here.
Where to put it, though? That's what I'm curious to see.
Right now mine will be hot, but that might change if my remote disconnect won't handle the load of the starter. I'm only doing this so I can put in the disconnect and use a Viper alarm to cut power to the car beyond the trunk at the same time I arm the alarm, not so I can put in an NHRA legal cutoff or something. If the disconnect wont handle it, then I will go to the Ford starter similar to your setup and run another line to the front to power the car.
In regards to being hot at all times, not sure why it matters if a 8 ga wire or a large starter wire is hot. If you cut the 8 ga wire you still have full battery power running into whatever you cut it with. I know the 8 ga wire has about a third of the amp capacity of a 1/0 gauge wire, but I suspect that just means the 8 ga wire will catch on fire at the same time it makes a big spark, while the 1/0 ga wire will just spark. :-)