Null && String Ops Again

I don't know enough math to demonstrate that any numerical operation
with a null should yield a null; although I would guess that it's true.
I just don't buy it, however, when dealing with strings and nulls. In a
simple table with first, middle and last name columns, I would infer
that a null value in the middle name column means the HR person forgot
to ask. A zero length string, however, tells me HR did ask and there is
no middle name. Regardless of whether HR asked, when I concatenate the
three fields, I can't think of a sound reason why I souldn't get the
first and last names.
Having now started a flame war, I actually have a question: How do I
set the default for any given database or table so that concat null
yields null is permanently off? I have tried exec sp_dboption
'myDB','concat null yields null',false (and many variations on
delimiting the parameters) but it doesn't do jack. I can use set
concat_null_yields_null off but that only lasts for the immediate
session.
I've tried to follow the thread through the BOL but I'm left scratching
my head on how to accomplish this.
Thanks.
Randy