Can this be done? Put a hidden nationality on nukes? I mean you can attack countries using hidden nationality and not go to war. Has anyone tried this with nukes yet?

I don't know, but that would be pretty unbalancing,

Secret WMD wonder?

I tested this concept and it works. I nuked two cities with a "hidden nationality" nukes and neither of the civs declared war on me. Unbalancing but interesting idea.

I was thinking of using a spy/terrortist with a suitcase bomb. The range of the unit would be one for bombing.

Also made a request for the Holy Hand Grenade of Antioch that would have been escorted to the outskirts of a city and then unleashed.

I think this has interesting possibilities... but horrifying implications... Civ2 had the option for suitcase nukes, but perhaps after 9/11 the game company decided discretion was the better part of valor... The problem with making HN nukes is two fold: First of all, even with high costs, there is no possibility for error... In other words, it works all the time. If there were some kind of rate of fire for this to give a probability of failure, it might be more balancing. The other problem is that, as with all HN units, there is no accountability for the attacking player. If you fail a spy mission and they find out who sent the spy, they might declare war on you... In fact, IIRC, in Civ2, if you got caught planting a suitcase nukes, ALL civs would declare war on you.... not sure about that though...