Lost in translation, not sure what the Vmca connection is. My reaction was to your
complete engine failure at maximum altitude and maximum continuous power? That will result in a far more demanding situation
Which I find to be the other way around. By his own description, the OPs required manoeuvre is about 3x more aerodynamically displaced than an EO situation at max alt & MCT.
I still take your word for it that as part of the certifying flight tests, full rudder sideslips had been tested all the way up there. Not sure what the limiter provides at M 0,8. Thank you for confirming my 3-degree hunch.