The UserPatch mod for the older CD release is really interesting, as it modifies the binary to give a lot of new AI script functions. Some of the ones for customized targeting have almost a declarative, map/filter feeling to them, such as `up-filter-range`. [1]

I think the newer versions of the C++ compiler are much more optimizing today than compared to what what Age of Empires II released on. I'd imagine it wouldn't be possible, or perhaps a lot harder, to make these AI mods with the Steam re-releases.

[1] http://userpatch.aiscripters.net/reference.html