hmmm, @Muda Muda No Mi, yeah, but I think BB already has the theory even before he got his Yami Yami no Fruit. And when he stolen WB's power, that was his first time.
When he fought Ace, BB said that his DF are unique and something about becoming the strongest. In that time, I began to think that his ability to sucks people and negates DF ability werent so special, after all he is relying on his fist to attack, not his DF ability. And Yami Yami no Fruit also didnt involved too much in his defense except from people with DF. Common logia fruit are generally stronger and better than his DF in terms of offense and defense.
So, what so special and unique about his DF are its ability to absorb other DF ability, that's why I think BB already has this theory that time. And about how to absorb, I think it is the opposite of Kuma's ability. If Kuma can repels anything, than BB can absorbs anythink.
And about cerberus theory, the base of that theory is one head per DF, right? But BB can use 2 powers at the same time (Chapter 577 page 14-15) with only one head.