Quoting just a small part of this post because it has the most important bit.
But...yeah it is a bad idea. Imo. I want to clarify first that it's not "nothing happens" which fail forward is avoiding. You get that without fail forward, when someone is hanging onto a rope and fails, or when the guards are on your heels and you fail to pick the lock, and so forth. The issue isn't with nothing happens.
Instead, it seems to be with failed rolls adding new information which was unrelated to the check to the narrative. For example, the lockpick fails, and now there is a cook. What's-his-names song doesn't make him feel better and therefore a guard shows up. That sort of thing.
The consequences here are logical--a cook could be in the kitchen, a guard could hear a song--but they aren't part of the check. (Compare--ok, you can sing, but there's a 20% chance you'll attract a guard, regardless of success/failure). There's a sort of double jeopardy going on. And this makes these games more, well, narrative--they're about telling a story more than playing a game.
It's fine if that's what you want. But it is opposed to what I want, and it's fair to recognize that.