What if the sadist looses the inclination to inflict pain ?
I’ve experienced periods (sometimes long periods) where, while I’m still intellectually interested in SM, I just haven’t been able to face actually running a scene. The culprits in my case have generally been worries, stress, tiredness or depression – basically the pressures of life getting in the way – and it’s never really been about my relationship or partners.
So bearing that in mind, I kinda like the suggestion of playful aggression. Since you say the vanilla side of your sex life is fine, maybe try rolling on top and holding his hands down or something. Pretty sure that’d work to kick me back into taking control TBH