Random Monsters Map Patcher – diverse neutral armies.

If they are completely random, then there's no other option. Simply, all random maps are built according to a template; the templates can just be chosen randomly during generation, or you can specify them in advance. In this regard, NCF creatures are easily generated randomly on any template. What I'm not sure about is how to more precisely define the conditions for the composition of units within the templates, and whether it's possible to somehow limit this. But I think it's worth figuring this out.

If we start placing NCF creatures, the map will be unplayable on the regular version.

On the regular version, one of the key aspects of your idea is lost, which is quite important. This raises the question: why even use it on the regular version?