For the 6NT example you don't need special rules, first ensure the bidding is correctly entered into GIB's simulation inputs ( I bet its not given 33 HCP in opponents hands and length in two side suits what other possible play could there be than cash your top two winners), then have GIB run more simulations say 100 (maybe some rule of thumb whether its enough for the given hand) before making the lead ensuring the lead still follows its leads database afterall that's just like humans who think a bit more with 3 hands hidden, if his partner is a GIB then it can run a few more simulations than normal with correct information gained from at least the lead and dummy. All that would reduce the rediculous stuff-ups without changing anything fundamental about GIB.