HelpOne question about Arma 2 and Arma 2 OA CD Keys

Hei again

So I've decided to buy another CD copy from Steam. My Arma 2 OA CD Key is banned by BE, but the Arma 2 CD Key isn't.

So I've made another Steam User to buy a new copy of Arma 2 OA, But not sure if buying OA alone is enough.
I have the Arma 2 itself installed and bought from my current Steam user (Let's call it X1). But is buying Arma 2 OA (not Combined Operations) on my X2 enough, or does X2 need to have Arma 2 itself in the Steam Library. Or will X2 use the Arma 2 files that have already been installed by X1.

I don't feel like paying another 20 bucks for CO when I can pay 14 for OA

And no, sorry, but I don't feel like buying keys for a few dollars here. Good offers, but no thank you.

All you need is a new copy of OA, since you don't get banned from regular ArmA 2