Let's look back on things that were cut or never implemented or abandoned for various reasons.

-matching ships mode

-blinking playfields

-striped playfields and backgrounds

-multiple ripple maps

-complex controls of the Destroyer shots

-variable range in helicopter shots

-numerous screens including giant galactic toilet paper

-kamikaze ship type

-invisible ships unless firing

-bomb drops when above enemy

-Easter egg where human falls out of explosion, crashes into wall and causes another explosion

-Easter egg using half the ROM to display my animated face

-Easter egg that displays the full color palette

-giant explosions

-screen flash on player death

-special explosion effect at game over

-32 color palettes got cut to 16

-ships on title screen moving up and down and also forwards and backwards

-bricks filling in the screen on manual matches that take too long

-crashing at edge of screen in auto flight mode

-explosion clipping

-sometimes ships are damaged but not destroyed

-different engine sounds for different ship types

-sound engine was greatly simplified

-more strategic firing for AI instead of continuous auto fire

-different sound pitch for p0/p1 shots and explosions

-inverted controls for vertical movement

-some alternatives for a 1 player mode where you had to fly through a series of obstacle courses with rippling screens and scrolling going on

-the same color palette would be used for 4 screens in a row

-mismatched shot and ship speeds

-hover in place AI state

-AI far scan

-smooth vertical scrolling

-vertical scrolling and ripple effect at the same time

-a user friendly select screen  

-complex flight path of ship in select screen

-mirrored ship doppelganger in select screen

-chunk of playfield on select screen demonstrating FX functionality

-horizontal and vertical scrolling in the same round

In the end I think I made the right choices with my cuts.