Glad you've enjoyed my game!
Some of these things definitely crossed my mind when I was working on this prototype. Unlocking new dungeons after reaching milestones is definitely the thing I want to add in the future, however, this might be somewhat finicky due to the engine limitations. Nevertheless, thanks for the ideas and references!
Answering your question: yes, randomness is a standard feature in Bitsy. I've done it through the shuffle lists tool, which basically allows you to add a bunch of different scripts in one list, and then the game will choose them at random.