Actually, Randy, I had your staging in mind when this thought hit me. Mine should be pretty easy to idiot-proof, and I'm thinking the way to do that is with the push button stop blocks you describe, to keep trains from venturing too far into the floaters, and by making the switch at the top of the helix a spring switch, so the natural preset is to the right. Another precaution might be to put a cross over from the outbound track back to the inbound, to allow an escape route back to the inbound track should the spring switch fail, or if a powered turnout at the top ends up being more practical. This would also facilitate the reverse move to clear a track in the event of an uncoupling.
With DCC, there's a greater possibility of something starting off in the wrong direction, since the operator controls the direction (and we all know my operators are usually pretty well-lubricated) but with a little planning and proper settings of the consists, that shouldn't be a big issue.
I'm also in the caboose camp, as well as a card flipper, so I'll be able to tell if a train is complete or not when it comes out of the hole.
I was able to check the two outer tracks (I need one more turnout to complete the other two) and the capacity works out to about 36 50' cars on track one, and 34 on track two, allowing for the three six axle diesels that would most likely occupy the space. David's suggestion of a switcher pocket has me thinking evil thoughts about using a helper to heft these big heavy trains up out of staging... The dispatcher could be the helper engineer....
Lee