DO NOT CHANGE THE GAMEPLAY!
Don't change a thing about the gameplay! The people complaning are NOT the people who gave you 5s and put you on the front page. People who voted 5 and didn't leave a comment loved the fact that SOMEONE posted a game that was CHALLENGING and FAST PACED. Whiney noobs are alergic to hard games, they want the "WIN" button to be placed in the center of the screen. Ignore them, DON'T YOU DARE SLOW IT DOWN.
Now for my complaints. Who's side is Bill on? He's killing the goombas, who are on the Koopa side, and he's knocking down the Koopa flag... but still his ultimate plan is to kill M&L?
Instead of goombas, you should have the powerup guys. Red and Green Shrooms, Power Flowers and Starman, or even Toads. Putting Starman in there as a target would be great, though the aforementioned noobs would probably wonder why killing him doesn't make you invincible. As for the flag at the end, you should be knocking down the one Mario raises in the castle after he yanks down the koopa flag.