I don't think this is correct. While the rules allow designating yourself as your companion for COS purposes, and thus flying as a Member and Companion on the same flight, I do not believe this will allow you to exercise your companion pass benefits while also claiming the benefit of another companion pass.

If Southwest were to allow you to do what you proposed, buy one ticket and daisy-chain the companion passes to get two additional seats for free, it wouldn't matter whether you were filling those two seats with one COS or two individuals. While the language quoted from the rules states "an individual may not travel as both a member and companion on the same flight execept in COS instances" the explanation that follows seems to limit "COS instances" to a person being his own companion, not to the situation the OP has described.