[Endoperez]

Do you mean their basic units or the special units available from the magic sites?

Basic units, something slightly more powerful than similar independents, wouldn't be overpowered even if other nations got access to them. It would give slight advantage to aggressive nation, though, which meant that a nation that conquered an enemy capital early could get access to types of units he couldn't normally get easily. Say, MA Mictlan getting Marignonese crossbowmen and infantry. A new poptype recruitment array would have to be created for most nations, but the idea is sound. There probably isn't particular reason for not including it.

The units from magic sites are special, often powerful, and clearly not something that other nations should get.