Hello there! :D Firstly, thank you for your very thorough review/feedback! That's too kind. :)
Absolutely agree with the scoring idea! I didn't have enough time to pop that in the end, but was thinking something to the effect of "time x people saved" would be a good scoring system! Perhaps bonus points from loot chests in the area (some found through one of multiple doors like you mentioned?).
I love the idea of saving trapped characters and extending the line! :D That and being able to release some small bursts of water (with limited amounts?) would be a really interesting dynamic. These are some really great ideas, very much appreciated! :D