I'd rather see the number of dwarves in each wave increased by two or three times. There's no reason that I shouldn't have 200 dwarves or more in my fort if I can feed that many as there have to be millions of them out there in any realistic world. The game also needs serious optimization so that you can run a fort with a thousand or so dwarves on a modern computer with no slowdown. Hack things out of the code that don't add anything useful like individual bodypart tracking and don't put them back in unless you can maintain performance.
If you honestly expect that, you don't know Toady...
Anyway, you are missing the point - the game is failing to provide meaningful challenges because all important resources are available in functionally infinite supply.
The game can only add meaningful decisions to the game when your resources are limited, and as such, you must learn how best to triage your needs with what little resources you have.
Again, the simplest resource to cut is labor.
For as long as dwarves are an infinitely replaceable resource, there will be no meaning to their lives, and you can freely send them out to die with no negative consequences. Play a fortress where you block out all migrants, however, and preserving dwarves becomes the highest priority, while managing what little labor you have effectively becomes the next highest.
You can set the population cap as high as you like, but the necessary ingredient is that migrants are not limitless and freely available. Limit the game to, say, 40 migrants total, and getting to 80 adult dwarves (through giving birth to and raising children alone), and you have given players a meaningful goal to strive for.
The current migrant system is basically a broken system, which, along with broken farming, broken stone/mining, broken metal production, and general broken AI and command/control systems means that the game functionally does not work as anything but a proof-of-concept.
Survival is supposed to be challenging, and Losing is supposed to be Fun, but the game, as it stands, is challenging only in as far as it is difficult to understand how everything actually works, and is easy as soon as you learn that. The game needs to be difficult at every stage, without the need for modding in greater and greater challenges, or just creating megaprojects.