When you think about it. Wouldn't just the normal and co-op play all be sorta Time Trails just they don't have the timer in them. And I think a restart button would be good. But maybe instead of it been the back button what if it was like pressing 2 buttons to restart. Like I'm sure it would be really annoying to be like right at the end of a level after trying for the last 3 hours to have your finger slip off the thumb stick and press the back button. It's a great Idea tho. I can see it been done. I would surport it.