This may be unpopular, but I miss when contracts were extended over multiple stages like in H2SA. Having multi-staged contracts and non-target missions helped add a sense of scale to the story.
Sure, some weren’t as good as the main levels, but I’d argue that stuff like Hidden Valley only sucks because it’s broken. I could quite easily see it being awesome in a remake of the game - although they could probably merge that and At The Gates together.