Sometimes I wish authors would post summaries of the themes and feelings they want to elicit. I feel like momomo often illustrates his futas as living the most enviable lives possible. As being so inhumanly lucky, horny, happy and successful that it's supposed to engender a feeling of frustration in the reader - like "oh, I wish that was me! That's so unfair!" Like the mini-story from page 64-69. It's more over the top in terms of creating the ultimately lucky and blissful character than most, but not by much. A fetish where the few most degenerate and horny monopolize every kind of girl, receiving every kind of pleasure, all the while living the most carefree lives possible.
Aside from the title of all of these futanari girls being "bad in the head" (immoral, etc) and every one of them in every work he draws being such terrible and depraved people, who are infinitely rewarded for their depraved antics, I really can't tell how intentional it is.