I'd say it should be an unsportsmanlike conduct penalty, but again, how can you prove that they are faking? The problem here is that the Giants players were so blatantly obvious that the league must take notice.
Here's my attempt at a solution: If play is stopped for an injury, the team can either A) use one of their timeouts, or B) the injured player cannot return for the rest of that series, rather than sit out one play like they do now. If the play they were injured on was the final play of the series, then he must sit out the following series that his unit (be it defense or offense) is on the field.
If the team uses a timeout, the player can return whenever he is ready. I think it would definitely cut down on the faking if a player knew he would have to sit out for awhile.