This is more food for thought than a suggestion, but it's still a suggestion.
One of the main problems with a lot of the suggestions that are suggested here is that they add complexity to the game. Now to some people, especially newbs, the game is complex enough as it is without adding more stuff into the game. But on the other hand there are a lot of people, like me, who want that extra depth.
I think that I'd better define what sort of complexity mean. A lot of new features don't really add depth to play, like the beekeeping industry. These add complexity, but they are optional, what I mean is that you don't need bees in your fortress, because there's something else far easier that you can do instead. The complexity that we need, and that this thread is dedicated to, is the sort that adds layers onto game play, the Improved Farming is one such idea.
The Improved Farming would be quite daunting for a noob, especially with all the other stuff going on at the very start of a fort.
My idea is that all these layers of depth are can be toggled as difficulty options, so when you gen a new world, you can select your difficulty options, not just number of animals, but game play features as well. You would be able to set it in the init file or something as well.
This would mean that noobs can master one game concept at a time, while advanced players can get their depth that they want.
I use the word depth as complexity implies that it isn't a good thing and that there needs to be an easier way to do it.
This suggestion doesn't really apply to DF as it is currently, since there's nothing that amazingly deep, maybe it could be applied to the military. This is more geared towards the future when more in depth things get added.