As the title implies, is there a way to allow the AI to use specific units while disallowing the human players from using those units? Or, is this more of a Mod thing?
Allow AI to use specific units, disable for players.
Offhand I'm not aware of any mod that has unit restrictions only for human players. I suppose someone could write one.
1 - If the game is going to be unranked, you can just ask people nicely not to do it, and refuse to play with people who won't cooperate
2 - You could disable the UEF nuke launcher but leave in the Cybran one.
This isn't perfect because it means the human players can't be the same factions as the AI. And it would be possible to "kidnap" an engineer or a factory in order to build nukes. But it would go a long way towards stopping humans from having nukes.
This could be done with a mod & could be done with a check of the player type to determine if the player is human or AI, so there would be no restriction on human players & AIs having the same faction, only humans having access to all the structures & units that the AI has access to.
I would suggest making a mod request thread in the Modding & Tools sub-forum.