The ship hulls should *do* something. Have some kind of ability. Like, the blue ones make the hitbox/projectiles a bit smaller (or something that makes dodging easier), the red ones could possibly block shots outright at a % chance, or get a damage reduction, and the green ones should use focus a little slower. I don't know. My thoughts.
This game is FUN because of the SATISFACTION you get when you find out your CRACKPOT IDEA actually worked... (e.g. Playing chicken between a pair of Dusters, 180-noscoping a Dart, taking down a 6-plane ambush with the Looper's Death Blossom...)
The third boss battle can be instant for a Wizard with the Rune of Focus, instead of spamming attacks and getting virtually nowhere, just run around and wait for him to spawn max henchmen, then use the Rune of Focus, and fire Energy Spark at the group. The shot will split several times between the group, which will include the boss. About 20 or so shots will hit the boss at the same time.
Instakill.
The emergency booster feels a little OPed. Use all your fuel to fly up, then the e-boost kicks in, leaving you perfectly horizontal. Then you just fall down and e-boost again when you're in a nosedive, and you are left horizontal again with plenty room to glide.