I checked back and there was a very similar patch nearly 4 years ago.
http://lists.gnu.org/archive/html/bug-coreutils/2008-10/msg00067.html
I think there was general agreement in the thread on its merits.

I wonder though, would a higher level option be more appropriate?
I think what's being configured here is whether to exit early on write error,
whether it is to one of the files or stdout. Why would you want
to treat them differently? Also you could get SIGPIPEs I think
if one of the files was >(a process).

The default would be to diagnose write errors,
and that could be changed with:

--write-error={[cont],ignore,exit}

cheers,
Pádraig.