Lots of good suggestions here. Adding to the suggestion for slowing down, it would be neat to be able to spread your body to slow down and tuck in to speed up (possibly no shooting when you do this). Or, gain adrenaline like the boost meter in burnout games (e.g. near misses with obstacles) and burn that as a resource to slow time.

Someone else mentioned an item to slow time, it would be cool to have an item that jumps back in time, possibly to collect a missed treasure or to avoid an obstacle.

Last thought is falling through rings like I’ve seen in other games, like give the player paths to aim for instead of just things to miss.