I think that a scoring system could be good, but I don’t think a par system would be a good way to go about it. Since rolls are random, and strategy is only half of the question as to how you would get the keys and get to the exit, your score may be completely different from someone else’s and it wouldn’t be a clear indicator of skill.
That being said, I am honestly not quite sure how you’d go about a scoring system in a game like this.