I’m actually thinking Riddler isn’t the goggle-masked duct-tape enthusiast at the start of the trailer, and is in fact coming to the crime scenes right after the killer’s done his thing to drop his own letters - “No More Lies” guy has his own reason for doing what he does, and Riddler has figured out who he is and why he does it, and is going to end up taunting Batman over knowing more than he does (so his “secret friend” thing is actually closer to the truth in terms of solving the mystery).
It would allow for a bit more flexible of a mystery format, because it would give Batman *two* mysteries/challenges instead of one - find the killer, but also find out how Riddler learned it and track him down.