I have thought about doing something similar, in adding another part to PAO, to bring it to an even number of parts. I thought about PAOS: Person/Action/Object/Setting, where setting is kind of a location within the location. I thought about setting up P, A, O and S for each letter of the alphabet, and then having a PAOS image for each 4 letters.
For example, I could have Michael Jackson/moonwalking/with a white glove/on a stage. Or Michael Phelps/swimming/in a Speedo/in a pool.
I never did do this, though, and instead, I'm now composing a letter pair list.
Just a thought