Today I've coded the individual pieces of that optional boss fight and started testing them. It's not fully working yet, but most of the stuff at least seems like it won't take much work to fine-tune to my liking.
That being said, I'm realizing now that boss fights could be a potential game-ending trap for the player; It's true that when you revive, if you had less than 25% of your health, I heal you back up to that amount as a goodwill measure, but that's not always enough. What if you just can't beat that boss yet? What if you're missing a few level or some gear before you can attempt that boss?
The game will always place you back in the room you last entered when you die. Should it place you in the room you left instead? Maybe that would be an easy way to fix this.
Time spent on the project so far: 668 hours
Currently working on: An optional boss fight + ending
Screenshot after the jump: Optional Security Six fight