simple question.

Is it possible to add Sahrani, OFP Islands, avgani, Aghan village etc. to ArmA 2?

Simple answer: yes.

http://forums.bistudio.com/showthread.php?t=84782

I have not tried it though so I can't help any more than to point you there. I believe Dec has used it.

CAA works very well. You can crank up the vis and settings on Sahrani w/out problems. There's a few model bugs, but overall, it works great. There's a thread here on SimHQ about it, as well (2 of them, actually).

Works well. It is a big DL though.

Watch your missions that you might use with CAA1. Some will CTD your ArmA2 (Sniper Trilogy). Some will never work because of unit addons, etc... (SimHQ, ACE,...) In the BIS forum thread it will tell you where to get the Avgani/OPX CAA1 addons to make those islands work.

Yes it is a big DL, but you are getting ArmA 1/Queens Gambit for free. You can't beat that.

Is this different than just dumping alot of your Arma .pbo's into an Arma2 mod folder?

I think the CAA1 mod cherry picks the necessary files out of the pbos, such as buildings and vegetation. I'm not sure dumping ArmA1 pbos directly into ArmA2 would have very good results. I'd say give the mod a shot if you are interested.