I thought you might be interested in looking at ARMA 2: CO (how to combine ARMA 2 into ARMA 2:OA and use together).
https://forums.bohemia.net/forums/topic/97608-arma-2-co-how-to-combine-arma-2-into-arma-2oa-and-use-together/?do=findComment&comment=1643367
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