Random Monsters Map Patcher – diverse neutral armies.

Even in a regular editor, you can create composite armies; you just need to find the right template. There are no synergies, of course (by the way, a combination of blue druids and light unicorns would look better). And there's nothing else, which is especially bad when it puts good and evil creatures into one unit.
The idea is very good, but it would be better to implement it at the template level, rather than with scripts that run when the map is loaded; it's just unnecessary complexity.