I just had an interesting idea for the game! Of course, it's just an idea; something for you to experiment with:
The breakout ball can now damage both you and the enemies. The enemies also slowly spawn more breakout balls into the game, instead of the bullet pellets it does now.
That's it! A relatively small change that could make the game feel a lot more intense. Your paddle becomes both your offense and defense, and the sheer number of balls at the end of any level will probably take care of stray enemies. What do you think?