I thought that another mechanic that can punish taking excessive long rests is if time actually went by, and the amount of "days" that you waste in act one had a repercussion on the story moving forward. It could be many things, like your situation with the tadpole getting worse every day, or that you miss on certain things or content if you don't beat act one in less than X days. You could also give away loot with some magical attribute that fades away, so if you want to have that +2 sword by the time you reach Baldur's Gate you better hurry up and make the most of each day cause the magic will fade soon.
