During possession, I think it's kinda a turn off that my pkemon is doing the possession and is talking to the player.
First, it feels like the story is more of fucking your own pkemon, so aside for the good visual material, it is not doing good in other factor as adult game.
Second, the charm of doing an adult act, part of it is seeing the partner reaction.
The current design of the possession completely nullify this aspect, and if any it's just seeing your own pkemon in complete bitch & servile state, which gets stale really2 fast.. At least, if the game shown the character reaction after the possession had passed, it would still be something.
If the one doing the possessing is also a human (and not a pkemon) it will also at least be something better than what we have now.
I mean, Imagine you are watching a porn of a male porn actor fucking a beautiful unmoving sex doll with no reaction. Do you think such porn film is a good porn material? Now imagine it worst, your pet dog is the male actor.
It's hard to explain, but hopefully, I get the idea acrossed.
Example of better settings:
When the possession happen, the target retain their own personality and might sometimes resist a little, but they follow the player's order. The pkemon will not interfere at all for the whole scene.