Personally, I think Kash could be a good choice. There is one thing holding me back on her, and it is the fact she did get very defensive in the WW game also and she was innocent, but I find it hard to believe she didn't know she was looking at the spreadsheet for the WW game, especially since she stated it right in the post that it was in fact the WW game...adding the fact she didn't bother to make sure she had a updated spreadsheet, especially since she was going to use it against someone to call them out as Mafia, adding to that the fact it had been mentioned who was WW in THIS game.
Ive already said Rich, FF and JS are others I would consider.
As far as the Ice/Pap thing goes. Yes, they could both be scum and using this as a way to look innocent. Although a BIG thing that keeps me from jumping more on that is...if Pap did get the invest and use it on Ice (which I do believe he did) and he was mafia, he would also know that the next person to get it could and most likely would use it on him to find out what he is.