Please excuse the odd title, but this crossed my mine as I was reading some alternate collision theories and their suspected survivability rate. Theoretically, could the iceberg itself have been used as a sort of giant raft, i.e. the passengers just sit on it and wait for rescue? It would alleviate the lifeboat shortage and underfilled lifeboat problem, at least to an extent. I assume blankets and linens could be taken and laid out on the iceberg to add some insulation, although the first class would probably never agree to the idea of sitting on a giant lump of ice in the Atlantic. Despite the fact that this is completely unrealistic because most would not agree to it, if they were willing to wait on the iceberg would it have been possible to do so without also contracting hypothermia from the cold of the ice and air, and could the iceberg have even been sat on? I'm not sure how jagged or flat it was, or how an iceberg of that size would be generally shaped.
If this could have happened, I think it would be best to have children and the elderly or sick on lifeboats, and able bodies on the ice, or have mixed groups in lifeboats and on ice and then switch after a time if possible to keep the cold of the ice from causing any extreme harm. Ideally class separation would not be a problem, although in reality it most likely would. Maybe the classes could be separated with certain lifeboats for classes, at least with designated "third class" lifeboats and mixed "first and second class" boats?
I believe the Titanic had actually left the iceberg behind a bit, but considering that some of the lifeboats rowed towards distant lights and made fairly good time in rowing, could they have possibly ferried people to and from the iceberg? I'm sure this would have taken time, but could it have been done? If Titanic had stopped right when it hit the iceberg this would probably be a much more effcient theory, but I think anything that might give a slightly better survival rate is better than the 1,517 deaths that took place due to underfilled boats and a lack of sufficent boats to begin with.