Sorry to have to break it to you buddy, but its already been done.
I am the suggester of a real BFH helicopter (which has alot of comments, and a hell'of'a lot of views). I had someone mod the Helicopter from BF2 in a while ago to prove how easy it was to put into BFH.
If you'd like a link to my thread, then just ask (xfire:sufferbaron)
However, I'm not saying its anything to stop you from modding this, just that its already been done, perfectly.