Dimensions

How wide is this staging yard going to be?  What scale are you modeling? Why is there only a foot of clearance?

You could feasibly switch HO or N with a foot of clearance so long as the yard is not too wide.  It'd be pretty darn difficult to see what you were uncoupling but, with a bit of practice, it's not impossible.  What could you change to increase the separation between levels?

-Johnny

Can you make it visible?

I do not like any track which cannot be accessed.  For that reason, I have chosen to daylight my staging yards, and have them right in the open in front of the fascia.  It works for me.

However, if you must have a staging yard which you cannot access easily, the only viable option I can see is to build a train on the nearest visible track and then run it into the staging yard.  Unless you can somehow reuse entire trains from one session to the next, you will have to spend some time switching between operating sessions.

Active Staging

I have a staging yard on a lower deck beneath the scenicked portion of the layout.  It's fully visible from the main operating aisle and trains are switched out down there to re-stage.  This activity occurs during the session, and is handled by a dedicated staging operator.

hidden staging

I have a staging yard that is 10 inches rail to rail below the lower deck. I have kept the sides open and for restaging I just back out the trains. There is about 8 inches of clearance and I can get my hand in and remove a car or loco if needed. I think 1 foot is workable.

Well, I've something similar:

Well, I've something similar: you can see it at first 3 pictures here:

http://valleybeforesilicon.blogspot.com/

About a feet from the top level is sufficient to put your hand and take a car / loco in N scale.

Additionally I can feed cars into tracks from the end of the stub.

In case I want to build a train, the idea was to switch the blocks between sessions in the visible yard in San Francisco (first picture) and then push the train in the staging.

The staging is visible from the inside of a "nolix", but I've installed a cheap camera (nearly 20 bucks) on staging ceiling, and a 7" lcd monitor on fascia panel.

Here is the LCD ( 33 euros makes the job!):

http://www.ebay.it/itm/ws/eBayISAPI.dll?ViewItem&item=250966222155&ssPageName=ADME:L:OC:IT:3160

but I'm sure you will find a comparable on Ebay or other eshops.

Hope helps.