I agree with your two ideas and the unfairness of the game. I am currently making quality of life changes to the game, such as the automatic power rerouting to the bullet shooter you have mentioned. It feels a lot better this way!
And fret not, I too found myself completely overwhelmed by the sheer amount of asteroids and their ridiculous speeds. Unfortunately it was something I overlooked in order to finish the game within the given time period. While this is not the best of excuses, I feel that your second idea, which revolves larger and slower asteroids, is a perfect solution to this issue. More time to react is wonderful, as I currently plan to keep the scanning feature and reroute delay just about the way they are, since I like the system-management aspect of the game.
While the concept might be good, I will not deny that unbalanced and unfair gameplay takes away from the concept. I will make sure to keep that in mind for future versions and future projects, and not rely heavily on concepts alone. Thank you very much for your thorough comment. It helped a lot!