I don't see why people think bringing Smith in for North would weaken the batting.
Smith basically couldn't be any worse than North. I'd back Smith to get runs ahead of North. He has the better first class average. On top of that, he's a gun in the field, and we've been absolutely terrible in the field in this match. Plus, Smith probably wouldn't be able to keep it as tight as North does when bowling, but I reckon he's the bigger chance to pick up wickets.
Has to be the most obvious selection call ever.