You could easily set a rather low cap for unicorn and deer and then make it dependent on wardens.
However, the Elvish economy SHOULD be simple.
Human economy should be versatile (think trade routes and market manipulation)... Elvish Economy should be "natural and sustainable", Orcish economy should be even simpler and more primitive than the elvish economy and should flourish only when being aggressive and looting.
Numbers can be tested and adjusted. It's a question of overall design philosophy.