"RBM" rbm2(remove wrote in message
news
He could put two GFCI outlets in the box and share the neutral on the
"line" side, but he can't install GFCI breakers and share the neutral,
it'll just trip the breakers

That's right. You cannot use regular GFCI breaker at the panel side of a
multiwire circuit.
However, there seems to be a special breaker called a double pole GFCB for
multiwire circuit. Judging from the lack of hits on google, it is probably a
rare item.

Here's some info I found:
http://www.petesdepot.com/522686.html
http://www.handymanwire.com/ubbthrea...&type=t hread