Mewtwo and Mew making themselves into presents is a pretty fun idea, lots of room to work in cream and ribbons, I might tweak is a bit to be their anniversary rather than the MC's birthday, since after chapter 4 a year will have passed in the story
Push ups could work, it would be easy to mix them with the squats since the MC just has to lay there
The whole "this Type has this fetish" concept, it could lead to some good ideas but I don't want to go too overboard with it, the AWC was easy to do since there's so many psychic legends and I can mix in some ghosts too. I might combine your idea of the Dragons having weak points with another idea someone suggested about giving the girls massages, there's loads of dragon legends to work with for that plan
I might do some smaller scenes with other types, but I'll need time to plan that out some more