If you do Store it in a session then you need to ensure that if you implement a web farm that the session is loaded correctly.
I am not quite sure why Session is a bad idea, if the client dose not need that backup copy, keeping the whole thing in server memory sounds the best; since the rest of the candidates are all sending from server to place (temporary) in clients' browser, and then get it back whenever client does any action. Situation is, whenever client ping back, server will unpack the encoded data (either in hidden field, cookie, url etc) and would possibly place in server again! It also waste bandwidth IMO.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.