With pleasure. Free and paid "neo retro" games with a lifespan of 4 hours is exceptional! You do a remarkable job.
The passport system is already more than enough, I go all out on the save states for the videos (saved me too much editing), but yes other difficulty modes are always welcome.
As for me, I am neither a collector or an Amiga owner, for the moment I have already made your game Dr Dangerous known to someone (one of my YouTube subscribers) who should buy the collector's version.
However, a middle ground could be possible via itch, by putting the extended rom on sale as some other developers already do. And good luck for the future, I will follow your projects closely.