Working my way through the Scapecast backlogs, and way, way late, but oh well!
For me, and I am most definitely travelling off the beaten path here, the steamiest scene was in Bad Timing, with Sikozu and Scorpius getting it on (or, perhaps more accurately, getting off) in the chamber. The whole 'To resisting our enemies/To not resisting our friends' exchange, and Braca looking on (the defocus was perfect, his commander and Sikozu together, in the center of his face, as he watches, unable or unwilling to join them) was beautiful, sexy, and one of my favorite scenes in the show.