Perhaps for overall easier ones that could still be hard in a bad situation:
"Make [Y] amount of product [X], then offer to caravans" (perhaps a bit too similar to mandates, but it should be easy unless you get "20 adamantine swords" or "30 featherwood figurines" in an evil region)
"Dig down into the caverns"/"Dig to the next cavern layer"/etc (rather variable depending on caverns danger, and it opens you up to new problems years after the fact)
"Secure breeding stock of animal [X], breed [Y] amount" (Perhaps a tad too hard if you get something ridiculous)
"Train [X] amount of preexisting fort animals for war/hunting" (should be simple if you have doggies)
Nothing that interesting, and I have no idea about specific punishments for each of them, but we could do with some safe-ish ones to fill the gaps so that we can occasionally "draw a card" and sigh in relief that you only have to make 30-odd wooden trinkets.
Also, inspired by religious ones above (due to many of my forts trying to incorporate shrines):
"[X] God has fallen out of favour, all depictions (statues, figurines, engravings, etc) of God [X] must removed (stored in some dank cellar or otherwise hidden away) and all shrines (or other public areas of worship) blocked off /hidden from liaisons/officials until the end of the year."
(I suppose any list should just have the challenges themselves, then Players could come up with roleplay reasons themselves, e.g: "Don't dig sideways into the surface of the mountain" could be read as "The King enjoys his view of these mountains, don't damage the surface with your mining, at least until he loses interest".)
I might be straying a wee bit too far off the original idea, but perhaps there could be a small chance of more long term challenges, such as having to do something over (or every) two years or maybe even four? They would probably have to have higher stakes/rewards.
And with that I conclude with my humble and none-too-original list of ideas. I'm quite interested in this, and would like to see what you lot come up with.