I was thinking in survival the rival male appearing could be a somewhat rare and random occurrence with the incoming male lions' strength also kind of random as well to reflect incoming males of various strength/experience.
Yeah, I can see that fight being a scripted sequence and if the new guy wins we get a message like "All hail the new King" similar to the stuff like "Family Pride" and "Hippo Dunk". If the original male wins it could be "The King Prevails" or something like that.
I would also think it could be interesting if we could lose a lioness occassionally, like if someone does not coordinate an attack on a cape buffalo very well and does not get 3 lions on it quickly enough, then they could lose a lioness. Example, if a lioness gets repeatedly stunned by the same buffalo, that should increase the odds of a fatality. If a lioness is lost, the player needs to get the meat meter back to the top and that will trigger a cub growing up and taking the place of a lost lioness.