I would think stability, but the downside of more parts that might break.
I had this idea of a multi-rotor with 16 motors, it's actually four identical quad-copters that stack together, 8 motors face up, the other eight face down, but they can fly independent of each other.
Anyway, I was thinking while it can split into four multi-rotors, it would also be sweet to lift something big.
Having four in one serves a particular purpose in my case.
I was just wondering if there are any obvious "no-nos" I'm overlooking.
I was thinking it would be like a master-slave deal when all four are "snapped-together"