Seems to me the bypass caps on the ends of the proposed piece of coax would
simply short the center to the shield at most R.F. frequencies.

So what this might just accomplish is to change the effective
length/thickness of the ground wire. I think there is a lot of confusion
between electrical safety grounds and R.F. "grounds" or counterpoises.  

Reason for having everything in the shack grounded to a common point and to
ground rods is so that electrical potentials won't build up between pieces
of gear and cause dangerous shocks. Whether or not we're dealing with close
lightning.

A ground from the second story is useless as an R.F. ground unless it just
happens to be resonant at a particular frequency. Whether or not such a
setup is of any use as a safety ground is probably the luck of the draw, but
I think I'd rather have the possibility of a working safety ground than not
should the big capacitor in the sky decide to discharge anywhere near by.

On the other hand, and this is just an off the top idea, How about a piece
of coax as ground wire with center conductors used as the actual ground. 
Now take the coax and wind a common mode choke in it at each end, but do
nothing with the shield at the top and ground the shield at the bottom.

Might just suppress common mode current flow on the outside of the coax.

Maybe we should write to the QST editors and ask for more articles on
grounding problems.

I have a friend, not a ham, who has written a series of books on "grounding
and shielding" published by Wiley.  He is now on his fifth revision of the
book.

When he gets it published, I'll see if Bookshare can get it from Wiley.He
has been a commercial consultant for years on instrumentation shielding etc.

Tom Fowle WA6IVG