Because SAG awards honor performers, its top prize is designated to "performance by a cast," collectively recognizing a group of actors featured in the same movie, as well as TV drama and comedy series.This year, the film nominees include four genuine box-office hits: "Black Panther," "Crazy Rich Asians," and two movies with a musical beat, "Bohemian Rhapsody" and "A Star is Born." (The fifth choice, director Spike Lee's "BlacKkKlansman," wasn't a slouch by that standard, but is the only one to have earned less than $100 million in the US.)Like any change to long-established tradition, an ensemble award — which has been proposed off and on for years — comes with various pros and cons.In the plus column, anything that puts more actors on screen and in contention is seemingly good for a show that only features four acting categories. The addition would also benefit movies with big casts that don't feature individual performers, more often a hallmark of the prestige dramas that garner lead actress or actor consideration.An ensemble award wouldn't automatically mean more blockbusters in the mix. A movie like this year's period drama "The Favourite," for example — whose three female leads have received individual nominations — would be a strong contender, as would a film like "Moonlight," the independent feature that snagged best picture two years ago.Still, the opportunity to recognize multiple performers clearly yielded a more populist sensibility from the actors guild this year, including a breakthrough for a superhero movie and a crowd-pleasing romantic comedy — both, notably, almost entirely populated by people of color.The main drawbacks to an ensemble award involve the logistics of it, starting with the arbitrary question of who shares in the trophies. The Academy of Motion Picture Arts and Sciences, which presents the awards, also harbors understandable concerns about diluting the honor, inasmuch as the obituary-leading designation "Oscar winner" would suddenly be dramatically expanded.At the same time, the Academy has already revealed itself to be contemplating changes, as the "popular film" debate revealed. And at least an ensemble category would come with the precedent that one of the major guilds has already embraced it.It's worth noting that the Emmys, too, have hardly been immune from ratings woes — like the Oscars, this year's ceremony sunk to a record low — and might be an even more logical fit for such an award, given the sprawling casts of shows like "Game of Thrones," "This is Us" and "GLOW."To be fair, the SAG nominees often feature an eclectic mix of contenders, including a few head-scratchers, and this year's roster is no exception. The gravitational forces at work, moreover, might be beyond any simple fix.Yet given the basic pressure awards shows face to entice more people to watch, expanding to include ensembles — opening the door to more actors, and potentially adding some life to the party — might be an idea whose time has come.