Thanks for all the replies, basically i made a assasin unit, that becomes available with guilds (at least thats my current thinking)
The unit is going to be a national unit limited to 3, with a very good withdrawl change and attack bonus into difficult terain
It's also going to be hidden nationality and always hostile
I was told in the better AI forum that pirate AI does not work for land units, i don't want the AI to build this unit, as defensively it's not all that great, same str as a maceman and does not get terrain def bonus's, it relies on speed and making hit and run strikes using it high withdrawl and terrain attack bonus to ambush units before pulling back
The AI is just going to build it like a normal unit, as it's a hostile unit (anyone can attack it with declaring war, like a privateer)it will likely get killed the second they leave there teritory with it, so i don't want the AI wasting money on a quite expensive unit, that it won't use effectively, thats why i was wondering if there is somthing you can put in the unit AI field that basically says don't build this