I lucked out and got the big, round peninsula but never really did anything with it cause I figured it was there for an in-game reason (similar to the secret beach). But since its been this long without any news and I feel bad leaving it to get overrun by flowers I've been meaning to do something better with it soon. Plus looking at the first post it seems like it probably doesn't have an in-game purpose since not everyone's peninsula is the same size or shape. So I'm probably going to move my island rep's house there so that 1) I don't have to worry about decorating a front yard for her since there won't be enough space anyway and 2) to open up some island space since I don't use the beach areas anyway.