I was wondering if anyone knows a way to permanently disable the creation of custom units?

I want to make a mod (preferably in a campaign setting) in which all races come with pre-made units, and a different tech tree. Making the units and related tech trees should be easy (if time-intensive), but the work would be useless if custom unit creation can't be turned off.

Now that im thinking about it, if i turn of all techs that provide weapons and armors I might not even have to turn it off .... hmmmm